Ramanathan and Almost-Black Carbon

My thanks to Nick Stokes and Joel Shore. In the comments to my post on the effects of atmospheric black carbon, Extremely Black Carbon, they brought up and we discussed the results of Ramanathan et al. (PDF, hereinafter R2008). Black carbon, aka fine soot, is an atmospheric pollutant that has been implicated in warming when it lands on snow. However, despite many claims to the contrary, atmospheric black carbon cools the surface rather than warming it.

There is an important implication in Ramanathan’s work regarding the canonical claim of AGW supporters that changes in surface temperature slavishly follow changes in forcing. Their claim is that the change in surface air temperature ( ∆T ) in degrees Celsius is a constant “lambda” ( λ ) called the “climate sensitivity” times the change in forcing ( ∆F ) in watts per square metre (W/m2). Or as an equation, the claim is that ∆T = λ ∆F, where lambda( λ ) is the climate sensitivity.

In R2008 they discuss the effect of black carbon (BC) on the atmosphere. Here’s the figure from R2008 that I want to talk about.

Figure 1. Figure 2C from R2008 ORIGINAL CAPTION: BC [black carbon] forcing obtained by running the Chung et al. analysis with and without BC. The forcing values are valid for the 2001–2003 period and have an uncertainty of ±50%. [Presumably 1 sigma uncertainty]

This figure shows the changes in forcing that R2008 says are occurring from black carbon forcing. Here is R2008’s comment on Figure 1, emphasis mine:

Unlike the greenhouse effect of CO2, which leads to a positive radiative forcing of the atmosphere and at the surface with moderate latitudinal gradients, black carbon has opposing effects of adding energy to the atmosphere and reducing it at the surface.

R2008 also says about black carbon (BC) that:

… as shown in Fig. 2, for BC, the surface forcing is negative whereas the TOA forcing is positive (Fig. 2c).

What are the mechanisms that lead to that re-partitioning of energy between the atmosphere and the surface?

Before I get to the mechanisms, I want to note something in passing. R2008 says that the forcing values have an uncertainty of ± 50%. That means the “Atmosphere” forcing is actually 2.6 ± 1.3 W/m2, and the “Surface” forcing is -1.7 ± 0.85 W/m2. This means that there is about a 30% chance that their “TOA” forcing, which is atmosphere plus surface, is actually less than zero … just sayin’, because Ramanathan didn’t mention that part. But for now, let’s use their figures.

PART I – What’s going on in Figure 1?

According to R2008, atmospheric black carbon causes the surface to cool and the atmosphere to warm. The surface is cooled by atmospheric black carbon through a couple of mechanisms. First, some of the sunlight headed for the surface is absorbed by the black carbon, so it doesn’t directly warm the surface. Second, any sunlight intercepted in the atmosphere does not have a greenhouse multiplier effect. Together, they say these effects cool the surface by -1.7 W/m2.

The atmosphere is warmed directly because it is intercepting more sunlight, with a net change of + 2.6 W/m2.

R2008 then notes that the net of the two forcings, 0.9 W/m2, is the change in the top-of-atmosphere (TOA) forcing.

The authors go on to say that because black carbon (BC) has opposite effects on the surface and atmosphere, the normal rules are suspended:

Because BC forcing results in a vertical redistribution of the solar forcing, a simple scaling of the forcing with the CO2 doubling climate sensitivity parameter may not be appropriate.

In other words, normally they would multiply forcing times sensitivity to give temperature change. In this case that would be 0.9 W/m2 times a sensitivity of 0.8 °C per W/m2 to give us an expected temperature rise of three-quarters of a degree. But they say we can’t do that here.

This exposes an underlying issue I want to point out. The current paradigm of climate is that the surface temperature is ruled by the forcing, so when the forcing goes up the surface temperature must, has to, is required, to go up as well. And vice versa. There is claimed to be a linear relationship between forcing and temperature.

Yet in this case, the TOA forcing is going up, but the surface forcing is going down. Why is that?

To describe that, let me use something I call the “greenhouse gain”. It is one way to measure the efficiency of the poorly-named “greenhouse” effect. In an electronic amplifier, the equivalent would be the gain between the input and output. For the greenhouse, the gain can be measured as the global average surface upwelling radiation (W/m2) divided by the global input, the average TOA incoming solar radiation (W/m2) after albedo. For the earth this is ~ 390W/m2 upwelling surface radiation, divided by the input of ~ 235 W/m2 after albedo, or about 1.66. That’s one way to measure the gain the surface of the earth is getting from the greenhouse effect.

Note that the surface temperature is exquisitely sensitive to the surface gain of the greenhouse effect. The gain is a measure of the efficiency of the entire greenhouse system. If the greenhouse gain goes down from 1.66 to 1.64, the surface radiation changes by ~ 4 W/m2 … on the order of the size of a doubling of CO2. Note also that the greenhouse gain depends in part on the albedo, since the 235W/m2 in the denominator is after albedo reflections.

Here is the core issue. For the “greenhouse” system to have its full effect, the sunlight absolutely must be absorbed by the surface. Only then does it get the surface temperature gain from the greenhouse, because some of the surface radiated energy is being returned to the surface. But if the solar energy is absorbed in the atmosphere, it doesn’t get that greenhouse gain.

So that is what is happening in Figure 1. The black carbon short-circuits the greenhouse effect, reducing the greenhouse thermal gain, and as a result, the atmosphere warms and the surface cools.

PART II – Almost Black Carbon

R2008 discusses the question of the 0.9 W/m2 of TOA forcing that is the net of the atmosphere warming and surface cooling. What I want to point out is that the 0.9 W/m2 of TOA forcing is not fixed. It depends on the exact qualities of the aerosol involved. Reflective aerosols, for example, cool both the atmosphere and the surface, by reflecting solar radiation back to space. Black carbon, on the other hand warms the atmosphere and cools the surface.

Consider a thought experiment. Suppose that instead of black carbon (BC), the atmosphere contained almost-black carbon (ABC). Almost-black carbon (ABC) is a fanciful substance which is identical to black carbon in every way except ABC reflects a bit more visible light. Perhaps ABC is what is now called “brown carbon”, maybe it’s some other aerosol that is slightly more reflective than black carbon.

As you might imagine, because almost-black carbon reflects some of the light that is absorbed by BC, the atmosphere doesn’t warm as much. The surface cooling is identical, but the almost black carbon reflects some of the energy instead of absorbing it as black carbon would do. As a result, let us say that conditions are such that ABC warms the atmosphere by 1.7 W/m2 and cools the surface by -1.7 W/m2. There is no physical reason that this could not be the case, as aerosols have a wide range of reflectivity.

And of course, at that point we have no changein the TOA radiation, but despite that the surface is cooling.

Which brings me at last to the point of this post. To remind everyone, the canonical equation says that the change in surface air temperature ( ∆T ) in degrees Celsius is some constant “lambda” ( λ ) times the change in TOA forcing ( ∆F ) in watts per square metre (W/m2). Or as an equation, ∆T = λ ∆F, where lambda( λ) is the climate sensitivity.

But in fact, all that has to happen to make that equation fall apart is for something to interfere with the greenhouse gain. If the efficiency of the greenhouse system is reduced in any one of a number of ways, by black carbon in the atmosphere or increase in cloud albedo or any other mechanism, the surface temperature goes down … REGARDLESS OF WHAT HAPPENS WITH TOA FORCING.

This means that the surface temperature is not simply a function of the TOA forcing, and this clearly falsifies the canonical equation.

In fact, I can think of several ways that surface temperature can be decoupled from forcing, and I’m sure there are more.

The first one is what we’ve just been discussing. If anything changes the greenhouse thermal gain up or down, the TOA radiation can stay unchanged while the surface radiation (and thus surface temperature) goes either up or down.

The second is that clouds can decrease the amount of incoming energy. It only takes a trivial change in the clouds to completely counterbalance a doubling of CO2. This is a major function of the tropical clouds, which counteract increasing forcing by forming both earlier and thicker.

The third is that the system can change the partitioning between the throughput and the turbulence. The throughput is the amount of energy that is simply transported from the equator to the poles and rejected back to space. On the other hand, the turbulence is the energy that ultimately goes into heating the climate system. In accordance with the Constructal Law, the system is constantly evolving to maximize the total of these two.

Fourth, the El Nino/La Nina system regulates the amount of cool ocean water that is brought to the surface, as well as increasing the heat loss, to avoid overheating. (One curious consequence of this is that the surface temperature in the El Nino 3.4 area has not warmed over the entire period of record … but I digress).

Part III – CONCLUSIONS

The conclusion is that the simplistic paradigm of a linear relationship between temperature and forcing can’t survive the observations of Ramanathan regarding black carbon. For the surface temperature to vary without changes in the TOA forcing, all that needs to happen is for the greenhouse thermal gain to change.

Figure 2. Single-shell (“two-layer”) greenhouse system, including various losses. S is the sun, E is the Earth, and G is the atmospheric greenhouse shell around the Earth. The height of the shell is greatly exaggerated; in reality the shell is so close to the Earth that they have about the same area, and thus the small difference in area can be neglected. Fig. 2(a) shows a perfect greenhouse. W is the total watts/m2 available to the greenhouse system after albedo. Fig. 2(b) is the same as Fig. 2(a) plus radiation losses Lr which pass through the atmosphere, and albedo losses ( L_albedo ), shown as W0-W. Fig. 2(c) is the same as Fig. 2(b), plus the effect of absorption losses La. Fig. 2(d) is the same as Fig. 2(c), plus the effect of thermal losses Lt. These thermal losses can be further subdivided into sensible ( L_sensible ) and latent heat ( L_latent ) losses (not shown).

We are interested in panel (d) at the lower right of Figure 2. It shows the energy balances.

As defined above, the thermal gain ( G ) of a greenhouse is the surface temperature (expressed as the equivalent blackbody radiation) divided by the incoming solar radiation after albedo. In terms of the various losses shown in Figure 2, this means that the greenhouse thermal gain G is therefore:

where

is the TOA solar radiation (24/7 average 342 W/m2) and

are the respective losses.

The important thing to note here is that if any of these losses change, the greenhouse gain changes. In turn, the surface temperature changes … and the TOA balance doesn’t have to change for that to happen.

127 thoughts on “Ramanathan and Almost-Black Carbon”

“Almost-black carbon (ABC) is a fanciful substance which is identical to black carbon in every way except ABC reflects a bit more visible light”
ABC exists. It is called dust. The plots of -LN(Dust) vs temperature over the last 800,000 years are quite revealing.

Willis Eschenbach: This is a major function of the tropical clouds, which counteract increasing forcing by forming both earlier and thicker.
Earlier than what? Thicker than what? And do you have a reference for that? I have written the same thing: increased CO2 might cause summertime clouds to form earlier and thicker than before, but for me it an unsubstantiated conjecture. Isaac Held’s simulations are potentially relevant to answering the question, but not yet. I don’t think I was the first to write that — you may have been, and I got the idea from reading your work. But here you put it as something known.

I note again the use of the ‘fuzzy word’ of ‘forcing’ (that I still do not find in my Physics book…) but at least this time we have a definition (in this context only?) of Watt/meter^2 that is a flux (per unit area) of a flow of Watts. That would make it a “power flux”. Then you talk about what happens over time.
So….
Are we talking Watts or Watts-time? Power or Energy?
One presumes what is really meant is that an “Energy Flux” (power over a duration flowing through an area) was intended, but that’s a presumption… And that is why I really would like to encourage using actual terms of physics rather than fuzzy headed “forcing”…
I’m now going to go back and try re-reading the article substituting “energy flux” for all the “forcings” and see if I can make any sense of it in terms of physics…
But for now, if I got the gist of it the first time through, it’s saying that if we go back to jet fuel with sulphur in it and with lots of ring compounds (that make nice soot) we can remove all the “global warming” from the surface in just a season or two. Nice, very nice… (The reason for using jets is to put it all at 40,000 feet or so and not near where people breath…)

Ok, so if sunlight doesn’t reach the surface then it can’t be re- radiated back at frequencies that are absorbed by CO2, which nominally happens in a short distance, hence surface warming?
A few questions –
1. What depth are we talking about? Cos on a hot day tubulent mixing will raise the totally mixed layer way high.
2. Doesn’t CO2 absorb in a narrow band? Hence reflected sunlight can’t be absorbed, hence albedo effect.
3. Does all re-radiated heat fit in wavelengths that CO2 can adsorb?
4. Isn’t the wavelength dependent on the temperature of the emitting body?

Very interesting. I’ll have to read it a couple of times to fully get it.
India is something of a natural laboratory for the effects of black carbon and not so black particulates. They accumulate in the atmosphere (troposphere) during the dry season and then get washed out by the monsoon. Most studies show surface cooling and upper troposphere warming during the dry season. Effects that at least partially reverse in the monsoon season.
Otherwise, How does time factor into this?

I’m usually not a suck-up, but Willis could immediately become the next Michael Crichton if he chose to go down that avenue. Supremely engaging writing skills and depth of knowledge and detail to back it up. Please consider it. Bling$$$ and a world stage to boot. : )

This is a major function of the tropical clouds, which counteract increasing forcing by forming both earlier and thicker.

Earlier than what? Thicker than what? And do you have a reference for that? I have written the same thing: increased CO2 might cause summertime clouds to form earlier and thicker than before, but for me it an unsubstantiated conjecture. Isaac Held’s simulations are potentially relevant to answering the question, but not yet. I don’t think I was the first to write that — you may have been, and I got the idea from reading your work. But here you put it as something known.

Earlier and thicker than they do when it is cooler. As for references, I have only my own work. The clearest demonstration is the TAO buoy dataset, see my analysis here.

Septic Matthew/Matthew R Marler says:
March 27, 2012 at 4:43 pm
…
Earlier than what? Thicker than what? And do you have a reference for that?

I realized my meaning might not be clear, I meant earlier in the day. The timing of the daily formation of tropical cumulus is a major thermoregulatory mechanism. See the discussion of the daily tropical cycle here, as well as in “The Thermostat Hypothesis“.
Also, you can see the clouds following the temperature in the albedo. This is from the ERBE data:
Note that when the Northern Hemisphere is hot in August, the clouds move up north of the the equator to Columbia and the area below the Sahel.
In February, in the heat of the southern summer, you get great masses of cloud below the equator in Brazil, as well as in the southern part of Africa.
So unless clouds are ruling the sun’s variations, that conclusively shows that increased temperature leads to increased tropical clouds.
Note the extent of the change in the albedo in say Brazil. By eye and by memory the seasonal change in the albedo is on the order of 30%. Given the incoming TOA equatorial insolation is about half a kilowatt per m2, a 30% change in albedo is cutting out no less than 150 W/m2 … which is why I call CO2 a third-order influence on the climate.
w.

E.M. Smith: You can see it happen any tropical day. As the sun rises and things warm, clouds form from the rising moist air. Days that warm fastest, end soonest in downpours. Days that warm slowly have slow cloud formation and less rain.
That I know. At least, I observed something like that in Hawaii, Taiwan, the Philippines, and central Missouri. I was wondering whether Willis might mean, as I have written, earlier and thicker with higher CO2. However, with reference to my “something like that”, is it actually documented that “early onset of downpours” is associated with the “rate of warming” earlier in the day? If you look at Willis’ data analysis, cooler evenings are associated with warmer mornings, and rate of warming does not specifically enter the analysis.
Willis Eschenbach: Earlier and thicker than they do when it is cooler. As for references, I have only my own work. The clearest demonstration is the TAO buoy dataset, see my analysis here.
I missed where your analysis of the TAO buoy dataset showed “earlier and thicker”. I am working on the TAO buoy data set to show (or perhaps test) the same thing. Granted, it is a fair inference from your Figure 2, but I have not yet confirmed that in any of the places I have looked so far.

One example of the ABC effect is the dust that frequently blows off the Sahara. It can significantly depress Atlantic tropical storm activity in Cape Verde area because it allows the atmosphere to be directly heated and retard the summer temperature rise of the sea surface. So not only does too little water evaporate off the ocean surface, the warm air aloft reduces convection between the surface and that level.

Willis Eschenbach says:
March 27, 2012 at 5:33 pm
I am glad that you wrote that follow-on post. I remembered at least parts of that analysis from when you first posted it. I have that and your TAO analysis bookmarked.
And back to my earlier question, you might have meant “earlier and thicker with greater insolation”. Obviously that can’t be unrelated to temperature, but one of the effects of increased insolation is increased H2O vaporization with little or no temperature increase (compared to what happens without water.)

Edit note: In R2008 theyhe discusses the effect
____________
How does the ABC cool itself? I assume it has its own emission budget to spend .. not all of which goes straight up.[Thanks, edit fixed. ABC cools itself in the usual way, radiation and conduction with air molecules -w.]

Very interesting Willis. Thanks. It deserves re-reading and close attention.
“For the “greenhouse” system to have its full effect, the sunlight absolutely must be absorbed by the surface.”, is the reason why Venus is not a victim of a “runaway greenhouse effect”.
If “the surface temperature is not simply a function of the TOA forcing, this clearly falsifies the canonical equation”. Brilliant!

Willis Eschenbach says: March 27, 2012 at 5:34 pm
A constant flux, in W/m2. In other words, watts per square meter as a 24/7/365 average.

Ah, I see, a non-physical hypothetical thing that doesn’t actually exist. OK, now I know why no actual physics term is used for it… (gets rid of those annoying variable 4th power radiation effects, the day / night temperature and humidity cycling and the enthalpy that goes with it, and so much more…)
Not tossing rocks at you over it, just at the persistence of non-physicality in the AGW “terms of art” and practice of “science as they know it”…
FWIW a “Forcing Function” (which is the only place I’ve actually found “forcing” to be a defined term outside of a logic proof) is a mathematical function where a property varies ONLY as a function of time:https://en.wikipedia.org/wiki/Forcing_function_(differential_equations)

In a system of differential equations used to describe a time-dependent process, a forcing function is a function that appears in the equations and is only a function of time, not of any of the other variables. In effect, it is a constant for each value of t.

So using ‘forcing’ to mean a time invariant constant value derived via an average is, er, possibly part of my “confusion”..
So, NOT a time dependent variation, but a constant flux. As Watts are power, not energy, we’re talking about a “Power Flux” OK, I’ll see if that interpretation maps to anything physical (though not ‘real’ as the real world has that power flux vary over all sorts of time dependent processes.)
This, BTW, does illustrate a bit more just why I find the usage of “forcing” such a PITA. It is simply an un-physical ‘hand wave’… How can one argue with a non-physicality? But, OK, back to the ‘Toy World’ with a constant power flux, no day, no night, no enthalpy changes, no…

If you warm the atmosphere and cool the surface, either or both of two things happen. (1) you kill convection, the clouds go away, the surface warms more due to less cloudiness, and the air-sea gradient is restored with a warmer surface, and/or (2) the surface sensible and latent heat flux into a warmer atmosphere would reduce, so the surface would lose less heat, and warm that way for a given solar forcing, until the surface temperature is warm enough again to restore the previous fluxes. I think the end balance is just the same because the surface will just warm to restore its original relation to the atmospheric temperature.

Though commonly seen in current climate research, the treatment of the atmosphere as a “solid” greenhouse shell is incorrect. This is to say that for a given volume of air with temperature T and surface area S, one can not simply calculate the energy emitted by the volume of air in the same way as it is a volume of solid object.
Another error in the article includes: “390 W/m2 upwelling surface radiation,” which is obtained by calculation of σT^4 with T being 15˚C (K. Trenberth). This is wrong because:
1) The earth ground surface is never a black body surface, one shall use equation ε σT^4 instead of σT^4, where ε is the overall emissivity of the earth ground surface, likely to be a figure close to 0.8.
2) 15˚C is the temperature of an air layer near the earth ground surface as a result of weather station measurements. As such it is basically the temperature of N2 and O2 that do not emit at whatever temperatures. One shall use the temperature of the earth ground surface 12˚C for this calculation.

E.M.Smith says:
March 27, 2012 at 4:53 pm
You and I both know that the use of the ‘fuzzy word’ of ‘forcing’ is not energy as in watts nor is it watts over time, in fact I doubt that “forcing” has any particular or specific meaning at all only that it sounds appropriate.
Such a wide variable can not be used in any other discipline where accurate readings are important.

Carbon of any gaseous form will be a low lying nutrient, it falls quickly when it is cooled and rises fast when it becomes warm, forests take advantage of this property, snow and Ice do Not, hold a UV lamp over snow, you will find that snow absorbs the UV, this does not mean a 100watt UV lamp produces 100 Watts of thermal energy back, don’t be incredibly stupid, even if it was made from carbon ice it couldn’t possibly do this.
If you’re so afraid of carbon in gaseous form why don’t you just stop using it! and please do let us all know how that works out!

“there is about a 30% chance that their “TOA” forcing, which is atmosphere plus surface, is actually less than zero …”
That’s true just from mathematical point of view assuming surface and atmospheric forcing are independent variables which they aren’t. Under assumption that studied particles are darker than the surface (i.e. convert incoming radiation to heat more efficiently), total TOA can never be less than zero.
“As you might imagine, because almost-black carbon reflects some of the light that is absorbed by BC, the atmosphere doesn’t warm as much. The surface cooling is identical,”
Wrong. Half of the reflected light reaches the surface, so surface cooling decreases as well.
“This means that the surface temperature is not simply a function of the TOA forcing, and this clearly falsifies the canonical equation.”
The canonical equation is only concerned about greenhouse gases and assumes not effects, but changes to other factors are negligible. To falsify the canonical equation, you need to show that changes (natural + anthropogenic) to other factors are significant enough.

“the canonical equation says that the change in surface air temperature ( ∆T ) in degrees Celsius is some constant “lambda” ( λ ) times the change in TOA forcing ( ∆F ) in watts per square metre (W/m2). Or as an equation, ∆T = λ ∆F, where lambda( λ) is the climate sensitivity.” [emphasis added]
My understanding of the claim is that an “enhanced” GHE (increased forcing but not @TOA) slows radiant heat loss from TOA, not an increase in “TOA forcing” (down-welling?). I’m not sure if anyone would agree with the “canonical” nature of the equation with a TOA limited forcing. In other words, I think you falsified an equation that’s not canonical with the forcing being limited to TOA.
I agree that [∆T = λ ∆F] is way too simple, at the very least λ is not a constant that we just haven’t been able to nail down yet. No, there are far too many “thermostats” in play over far too many different time intervals for such a simple linear response; rotation, seasons, cloud formation, PDO, sphere (cold poles-hot equator), Milankovitch cycles, etc. that can easily dump “excess” heat (lol) to space.

Willis-
Thanks for another great post. As I have said before, you always make me think.
.It bothers me that the CAGW modelers always talk about black carbon. Yet don’t define it. There are lots of particles and aerosols in the air. When light strikes a particle it is either absorbed or scattered. The amount absorbed and scattered is expressed by the complex index of refraction. Different particles have very different refractive indexes. Different forms of carbon even have different refractive indexes. The value of the complex index of refraction should be the begining of the model input. Yet you never see that value mentioned. I ran across a survey paper that covers a great deal of the physics of particles as it relates to climate models. If you haven’t already read it, it might be worth a look:http://www.peer.caltech.edu/Particulate/Aerosol/mines/Light%20Absorption%20by%20Carbonaceous%20Particles-Review_Bergstrom_AST_2006_39_1.pdf
Incidentally, the paper gives the following definition of climate forcing.
“Climate forcing is most often defined as the change in net
radiative flux at the tropopause attributable to a specific component.
A positive forcing is an increase in flux, tending toward
warming of the Earth-atmosphere system. Forcing is so called
because it is an input to the system determined by factors outside
it. Figure 1 shows how the change in radiative transfer is
determined from atmospheric concentration of light-absorbing
particles. Most climate modelers first assume physical properties
(size, shape and state of mixing, categorized as morphology)
and a refractive index, obtain scattering and absorption cross sections,
and apply those properties to modeled concentrations. A
few models of global climate have examined effects of differing
morphology (Haywood and Shine 1998; Chung and Seinfeld
2002) by comparing climate forcing calculated with different
assumptions”.

Willis-
One other comment. While I dislike pedantry, I do think you need to change the sentence above your equation defining “G” from:
….the thermal gain ( G ) of a greenhouse is the surface temperature divided by the incoming solar after albedo.
to:
….the thermal gain ( G ) of a greenhouse is the surface radiative flux divided by the incoming solar radiative flux after albedo.
Since all the terms in the equation are in watts per square meter.[Thanks, I’ve clarified the main text. -w.]

I can only imagine the narrative of a future documentary.
Earth.. The only planet in our universe that is warmed by coolant. Controlled by forcings of an unspecific nature, warmed by media cycles that seem to follow seasonal variations that are governed by solar influences, solar influences that are out right dismissed.
EARTH.. Ship o’ fools. Exclusive to channel WUWT.

… FWIW a “Forcing Function” (which is the only place I’ve actually found “forcing” to be a defined term outside of a logic proof) is a mathematical function where a property varies ONLY as a function of time:

In that case let me assist you. Here’s a whole page defining the term, from the IPCC report …

2.2 Concept of Radiative Forcing
The definition of RF from the TAR and earlier IPCC assessment reports is retained. Ramaswamy et al. (2001) define it as ‘the change in net (down minus up) irradiance (solar plus longwave; in W m–2) at the tropopause after allowing for stratospheric temperatures to readjust to radiative equilibrium, but with surface and tropospheric temperatures and state held fixed at the unperturbed values’. Radiative forcing is used to assess and compare the anthropogenic and natural drivers of climate change. The concept arose from early studies of the climate response to changes in solar insolation and CO2, using simple radiative-convective models. However, it has proven to be particularly applicable for the assessment of the climate impact of LLGHGs (Ramaswamy et al., 2001). …

Read the whole page, it lays out the way it is used in the field of climate science. I know you don’t like “forcing”. I don’t either. But that’s what’s used in climate science … so you might as well get used to it.
w.

E.M.Smith says:
March 27, 2012 at 4:53 pm
You and I both know that the use of the ‘fuzzy word’ of ‘forcing’ is not energy as in watts nor is it watts over time, in fact I doubt that “forcing” has any particular or specific meaning at all only that it sounds appropriate.

Willis Eschenbach says:
March 27, 2012 at 11:10 pm
“you nor E.M. Smith have done your homework.”
Willis, Cut the crap mate! (is that too strong?) When did your world revolve around the IPCC or what it has to say. I haven’t been giving any home work lately by the IPCC.
I do try, I think you have a good understanding of these issues, and you are an excellent educator, and that is why I like to pick you brain every so often. We can only kick a dead horse so many times!

Carbon of any gaseous form will be a low lying nutrient, it falls quickly when it is cooled and rises fast when it becomes warm, forests take advantage of this property, snow and Ice do Not, hold a UV lamp over snow, you will find that snow absorbs the UV, this does not mean a 100watt UV lamp produces 100 Watts of thermal energy back, don’t be incredibly stupid, even if it was made from carbon ice it couldn’t possibly do this.

“Carbon ice”? “Carbon in a gaseous form”? “100watt UV lamp”?? My friend, I fear that makes no sense. I said nothing about any of those.

If you’re so afraid of carbon in gaseous form why don’t you just stop using it! and please do let us all know how that works out!

You misapprehend me and my post entirely. There is nothing in it about “carbon in a gaseous form”. It’s about an aerosol (fine particulate matter suspended in the air) called “black carbon”, which is also known as soot, as I stated in the third sentence.
So I fear I don’t understand what you think I said about “gaseous carbon”, since I said absolutely nothing about it.
You go on to say:

I can only imagine the narrative of a future documentary.
Earth.. The only planet in our universe that is warmed by coolant. Controlled by forcings of an unspecific nature, warmed by media cycles that seem to follow seasonal variations that are governed by solar influences, solar influences that are out right dismissed.

Dang, spaceman, you are a long ways from Earth. Again, you seem to be talking about another post than the one I wrote, even another planet. Let me strongly suggest that if you disagree with something I’ve said, QUOTE MY WORDS EXACTLY. I said nothing about something being “warmed by a coolant”. I said nothing about media cycles. Where does this stuff come from?

EARTH.. Ship o’ fools. Exclusive to channel WUWT.

Can’t help you with that. I don’t know why you are on a ship of fools, why you are calling EARTH on your ship’s radio, or why you have opened an exclusive channel to WUWT.
But now that your exclusive channel to WUWT is open, my suggestion would be that you use it to actually discuss the issues and ideas. If you disagree with me, then quote my words so we both know what you are talking about. That way we avoid misunderstandings.
Because I can defend my own words, and I’m happy to do that, to explain and defend what I’ve said.
What I can’t and won’t do is to defend your misunderstandings and fantasies about what I’ve said.
Thanks,
w.

“there is about a 30% chance that their “TOA” forcing, which is atmosphere plus surface, is actually less than zero …”

That’s true just from mathematical point of view assuming surface and atmospheric forcing are independent variables which they aren’t. Under assumption that studied particles are darker than the surface (i.e. convert incoming radiation to heat more efficiently), total TOA can never be less than zero.

It is generally accepted that reflective aerosols cool both the surface and the atmosphere.
And, as R2008 points out, black aerosols cool the surface but warm the atmosphere.
On my planet, that shows that surface temperature and atmospheric temperatures are independent variables. Don’t know how it works on yours.
w.

@WIllis:
No, I don’t need to ‘get used to it’. Though I do appreciate the pointer to where they have made up some jargon. Jargon, however, is not physics. It still needs to be converted back to something that is a physics term set in order to have any hope of solving a physics problem.
I might as well define a Royal Phisbin as when the earth cools by a net negative energy flux from human mass to planet mass ratio and then declare the globe cooling as human mass is increasing. We simply don’t get to “make it up as we go along”.
So again, thanks for the pointer to where the made up term first is defined. Now we’re up to what?, three variations on what it might have meant so far? W/m^2 then (Average standard W/m^2) and now it’s a whole formula:
‘the change in net (down minus up) irradiance (solar plus longwave; in W m–2) at the tropopause after allowing for stratospheric temperatures to readjust to radiative equilibrium, but with surface and tropospheric temperatures and state held fixed at the unperturbed values’
(But without any statement about averaged over some long time period…)
So, please refrain from accusing of “failure to do homework” when you have given me 3 different statements in the same post…
I’ll now go back and TRY to re-read what you wrote sticking in the paragraph version of “forcing” to see if there is any added ‘reality’ injected by it; but on first look it’s not encouraging.
We’ve got a ‘down minus up’ that needs clarification, then we have “longwave” that’s a bit vague, now we also have a ‘tropopause’ (that tends to move and wander – and is not a fixed layer anyway as it has eddies, tears, and convective plumes that put dents in it; oh, and altitude varies with latitude) effect to try to figure out what THAT is in SI units and after that we get to ponder “readjust to radiative equilibrium”… and then a “hand wave” to “Surface and tropospheric temperatures and state held fixed” when no such fixed state exists…
So again I’m left at exactly the same point: “Forcing” is an aspirational statement and NOT physics. Nice for making hypothetical “toy worlds”, but disconnected from reality. Fine for what is expected from “climate science”, but I think your work is typically far beyond them and has a good handle on physics and reality anchors. Thus my frustration when you let their “fuzzy terms” crawl into your normally clear and clean thinking.
In essence, the latest “definition” of ‘forcing’ given here is a statement of a toy world state and is not physics. A term for how parameters are to be set in a computer model, but not a statement about how the world works. Not anchored in SI units nor in physics, but anchored in a toy world where one can have “Surface and tropospheric temperatures and state held fixed” in an algorithm; unlike in reality.
Again, I’m not tossing rocks at you. I’m just trying to map the posting to physics as I learned in college and translate any “local jargon” to what it means in that system, if anything. Finding that it’s “Unphysical” is just fine with me. It means I can not bother expecting any actual ties to reality. Ive done programming and I can play with ‘toy worlds’, I just prefer not to confuse them with anything real.

Willis Eschenbach says:
March 27, 2012 at 11:40 pm
I enjoyed every moment! do you feel good now? bringing up irrelevant argument’s, soot, fine particles, who cares? you’re not in any danger, I know these things! ha! Classic Willis!! spaceman? funny!

Willis, Cut the crap mate! (is that too strong?) When did your world revolve around the IPCC or what it has to say. I haven’t been giving any home work lately by the IPCC.

Thanks, Sparks. My point was that “forcing” and “radiative forcing” are not some undefined term as you and E.M. Smith foolishly claimed. When I said you hadn’t “done your homework”, I meant that a simple google search would have brought up lots of definitions, someone gave another one above.
I chose the definition from the IPCC glossary because for all the faults of their reports, their glossary reflects how the words are used in the field. But I could have chosen other definitions … as you could have done as well, if you’d done your homework before claiming that there was no definition for the term.
Regards,
w.
PS—You ask, is “Cut the crap, mate!” too strong?
Well, no, if you are right it’s likely not too strong.
When in fact you haven’t done your homework, however, it’s way, way too strong …

Very thought-provoking. And very well presented too. I have also just read the two sister articles you linked to (it’s not about feedbacks; Thermostat Hypothesis). A lot to take in but just quickly (and at the risk of appearing foolish) I wonder if you have considered whether some of the concepts/ ideas central to complex systems analysis might be prove useful in helping you develop your hypotheses further?
For example, your descriptions of clouds/storm clouds/storm systems (heat engines) could describe the interacting agents that characterise complex systems – with information flows between agents consisting of eg., heat energy flux, wind/ air/ water vapour movements; threshold phenomena, self-organisation and spontaneous assemblage are also important feature sof many types of complex system (biological as well as non-biological) and emergent behaviour(s) eg. that generate stability, adaptation, and evolutionary change at a variety of spatial-temporal scales… just a thought.

@WIllis:
No, I don’t need to ‘get used to it’. Though I do appreciate the pointer to where they have made up some jargon. Jargon, however, is not physics. It still needs to be converted back to something that is a physics term set in order to have any hope of solving a physics problem.

Yes, you do need to get used to it, because the term is widely used in the field, and the field is not going to change to fit either your preferences or my preferences. You want fun? You think those definitions are inadequate? Take a look at the subdivisions of forcing. Here’s enough to give you a flavor …

We employ several alternative definitions
of radiative forcing, for the sake of characterizing the
forcing agents better and aiding interpretation of the climate
responses that they evoke.
[16] The simplest forcing, and the only pure forcing, is
the instantaneous forcing, Fi. Fi is the radiative flux change
at the tropopause after the forcing agent is introduced with
the climate held fixed. The reason to use the instantaneous
flux at the tropopause, rather than the flux at the top of the
atmosphere, is that, as shown by Hansen et al. [1981], it
provides a good approximation to Fa, the flux change at the
top of the atmosphere (and throughout the stratosphere)
after the stratosphere is allowed to adjust radiatively to the
presence of the forcing agent.
[17] The adjusted radiative forcing, Fa, might be expected
to be a good measure of the radiative forcing acting on the
climate system and relevant to long-term climate change.
The reason to anticipate this is that the stratospheric
temperature adjusts rapidly, in comparison with the response
time of the troposphere, which is tightly coupled
to the ocean, and most forcing agents are present longer
than the stratospheric radiative relaxation time. Thus Fa, the
flux at the top of the atmosphere and throughout the
stratosphere after the stratospheric temperature has come
to radiative equilibrium, is the principal measure of climate
forcing employed in RFCR and by IPCC [2001].
[18] Ultrapurists may object to calling Fa a forcing, and
object even more to forcings defined below, because they
include feedbacks. Fa allows only one climate feedback, the
stratospheric thermal response to the forcing agent, to
operate before the flux is computed. The rationale for
considering additional forcing definitions, which allow
more feedbacks to come into play, is the desire to find a
forcing definition that provides a better measure of the longterm
climate response to the presence of the forcing agent.
Specifically, we seek a forcing that is proportional to the
equilibrium global temperature response, with the same
proportionality constant for all forcing agents. For the
reason mentioned above and illustrated in RFCR, Fa tends
to provide a better indication of the global climate response
than Fi. Because …

blah, blah, blah …
They go on to define other forcings, Fg and Fs, read the paper for the whole gory account.
I don’t like it, you don’t like it. But the terms are an unalterable part of the jargon of the science. Can we move on?
w.

Willis Eschenbach says: March 27, 2012 at 11:55 pm
Thanks, Sparks. My point was that “forcing” and “radiative forcing” are not some undefined term as you and E.M. Smith foolishly claimed.

Willis, I never said it was “Undefined”, I said it was a ‘fuzzy term’, and it is. You have given 3 variations on what it meant. And I did do a web search. Found two definitions, neither of which was the IPCC report.
And no, I don’t ever need to get used to it. I “keep a tidy mind” and physics is in one box, ‘fuzzy terms’ in another. I will never allow an untidy idea to assert dominance in tidy areas, like physics.
As I noted above, I’m quite comfortable using it in the “term of art, unphysical, tied to toy world modeling” sense (now that we have that IPCC description). But it will never be allowed into the “physics” or “reality” boxes based on the clear statements of unreal steady states in the definition.
It will, though, always raise a “unreality” flag (in my internal narrative while reading) for any work where it appears as it is based, by definition, on non-real conditions, as you quoted above. For that I thank you.
Per it being embedded in the ‘science’ so must be adopted and internalized: Must we then adopt uncritically and unquestioned such things as aether and phlogiston? They, too, were created terms of art accepted in their day… That is why I ‘keep a tidy mind’ and do not let just any old term crawl in and take over in the tidy parts.
Per “can we move on”: Certainly. I now have what I originally requested, a definition of what this ‘fuzzy term’ is (presuming you are using the IPCC version and not the ‘average W/m^2’ one) and I’m now trying to work out what is the closest thing to reality that might mean as I re-read your work in that context. ( I was happier with W/m^2, BTW, it’s a direct translation without unphysical steady states…)
In general, I “think you have it right”; but I think it would be more authoritatively shown with an exposition using energy flux and not “forcing” with it’s explicit non-physical anchors. Sticking in “W/m^2 in a very short time period as an approximation of a steady state” I think gives a conclusion that is the same as what you got, and is, I think, correct.
Basically, black soot in the air intercepts energy flux and warms the air, prevents it from reaching the ground, which cools. Then looking at it as grids gives a very similar result for all non-polar cells. ( I’d not gotten to the point of thinking about what happens at polar areas with sideways lighting nor ‘the dark side’ yet, then that whole IPCC non-physical toy world definition intruded with yet another iteration…)
So, “moving on”, for me is to use the “W/m^2 very short time slice” to verify a physics based view; then try figuring out what the ‘toy world’ view would be (and is there anything to reconcile between them). The first on the “tidy” side, the second on the “IPCC” side of mind…
Or, short form: From the definition in the IPCC report I know that they aren’t talking about physics, so I can “move on” from even trying to make anything physical out of it. It is a ‘toy world of unreality’ and I can “move on” to just expecting it to be a made up world model…

Willis Eschenbach says:
March 28, 2012 at 1:17 am
Sparks: Can someone who has an active interest in science be accused of not doing their homework?
Willis: “Depends on whether they’ve done their homework, doesn’t it?”
No. the statement does not depend on if home work has been done or not. it implies that it has been done. Doesn’t it?

If it is assumed the average cloud temperature is -19 deg C, radiation from a 15 deg C Earth to clouds is only 155 W/m2 for the 70% of Earth with cloud cover, rather than 390 W/m2 surface radiation as claimed. How does this effect the model ?

Willis Eschenbach says:
March 27, 2012 at 11:46 pm
…
On my planet, that shows that surface temperature and atmospheric temperatures are independent variables. Don’t know how it works on yours.
____________________________
Now you have successfully built up a strawman and beaten it to death.
Any argument can be proven wrong when put into a different scope. But I was talking about your statement on the paper which is about effects of black carbon, not about reflective aerosols. And in scope of forcing caused by black carbon particles, surface and atmospheric forcings are not independent variables.

Steve Richards says:
March 28, 2012 at 1:41 am
The discussion here between Willis Eschenbach and E.M.Smith proves the worth of WUWT.
I suspect many readers have learnt from this discourse.
——————-
Well, I for one have learnt a great deal from these people who very clearly know an enormous amount about the physics of the Earth’s climate and are generous enough to post here on WUWT. They have my gratitude.
What about you Steve. Maybe you could show us some of your moves… ?

For all the recent learned discussion of black, and almost black, soot I don’t seem to recall it being mentioned much until recently when we needed something else to explain away differences between observed and predicted or why we’re all going to die from global warming without it warming. So, where does one find the studies of the annual generation and deposition of black, almost black and any other kind of soot? And where does one find correlations between that and observed phenomena?

I’ve said it before — the effect of BC depends on where exactly it is. It warms the area where it is present, and cools any atmosphere (if any) below it by intercepting/absorbing sunlight from above. If it’s on the surface, it warms that & then by convection/conduction the air above it.
Obviously some falls out on the surface — that causes surface warming. Any in the air warms that air — either high up or right near the surface. So where is most of it?
I can’t say for sure, but working at a coal plant for yrs, I know a bit about BC. Typically the blackest BC flyash particles are the heaviest, and smaller, more completely burned ones are lighter both in weight and blackness. So my SWAG is that much or most of the blackest BC spends little time in the air & deposits on the ground fairly quickly. Lighter, grayer particles are more mobile, and the lightest (almost whitish) particles have the longest “air time”. I’d think that most BC from diesel vehicles reaches the ground very quickly.
So it seems like BC can cause both surface cooling and warming, depending on where exactly it is. What the final word on the subject is, I don’t know.

Willis, I find the article deeply disturbing, in part because I think upwelling/downwelling radiation models are virtually impossible to get right without solving a diffusion equation (which nobody does AFAICT), in part because the carbon discussion seems to ignore gross first order effects AND radiative diffusion in the greenhouse bands (where the height the atmospheric carbon absorbs sunlight matters), compounding the error.
For example, suppose the carbon particulates for some reason were concentrated near the tropopause — in that case atmospheric warming there would be radiated out preferentially and would block the surface, resulting in net cooling of both surface and atmosphere. Suppose they are a thick layer at the very bottom of the atmosphere. Now the atmospheric warming is in direct thermal contact with the ground and might well amplify the surface temperature and the atmosphere all the way to the tropopause. Suppose it is “uniformly” distributed in the atmosphere up to the tropopause. Now one gets a different result again, because now all of the atmosphere warms, with the top warming slightly more than the bottom and the ground differentially cools. Distribution matters, and particulates presumed large compared to an air molecule will not behave like a “gas” — they will probably exhibit a very distinct gravitational sorting with larger particles and greater density nearer to the ground.
Note well that anyone who has flown into a city has seen the soot from the many, fires below and it is by no means concentrated uniformly — it tends to form a thick layer somewhere in between ground and tropopause, often close to the level where clouds are trying to form. This is no coincidence, of course.
Particulates/aerosols also nucleate clouds out of saturated air, so the soot — depending again on particulate size and density — have a positive effect on albedo. Albedo takes a bit “off of the top” of TOA incoming radiation by reflecting it out. Even a tiny increase in albedo would a) increase the surface cooling and b) completely cancel the atmospheric warming because clouds have a much much higher albedo than transparent, cloud-free air with or without soot until the soot reaches the level of being “smog”, that nasty mix of soot and condensing moisture see note above.
Of course particulates smaller than a certain size (50 microns?) aren’t likely to stably nucleate water droplets and are more likely to be lofted and mixed more uniformly into the air. Soot that does nucleate a cloud (and for that matter, ambient soot too small to participate in the actual nucleation is often scrubbed out of the atmosphere in the ensuing rain. Remember there is an electrostatic force between soot particles of any size and a water droplet in a cloud, and once a particle is captured it doesn’t get out.
Soot is also produced in highly localized places and is nowhere near uniformly distributed in the atmosphere. Some of the places it is produced have a high average humidity, some don’t. The local air currents where it is produced vary, carrying one day to the North, the next to the Southwest, to rain out when it goes Northeast but to get carried far far away when it heads South. How high it gets, how the particulate sizes get sorted out in different atmospheric layers in different directions over different areas, depend in detail and highly nonlinear ways on the entire complex of “weather” — wind speed, direction, humidity, rainfall, cloud cover, temperature.
Finally, soot that deposits on ice or snow has a profound local warming effect on the surface, by directly decreasing the surface albedo, where almost anywhere else it is irrelevant. Furthermore, the warming effect is often delayed — at the heart of every snowflake is (often, usually) a tiny speck of dust or soot. Surrounded by ice, it absorbs little light and has a very small warming effect (the ice/snowflake is net neutral-to-cooling because of its high albedo whereever it falls). However, if snow ever starts to melt in bulk, the dust accumulates on the surface, greying the snow surface as it melts and reducing its albedo. The more snow that has melted, the greyer the surface, the faster the rest melts. Not only nonlinear, but non-Markovian (highly dependent on the recent thermal and precipitation history of the venue). Anybody who has lived in the cold north knows that in spring when the snow starts to seriously melt, it all gets “dirty” from the embedded particulate matter, which speeds up the melt.
The article alleges that “almost black carbon” nucleates clouds but “black carbon” does not so that one is (maybe) cooling and the other is (maybe) warming. It alleges that the monsoon is being affected by it negatively, and yet the figures of the article itself do not substantiate that — in Africa and China it is linked to more rainfall where it is produced, in North Africa the rainfall is reduced even though there is little black carbon produced there or present (suggesting that the cause has nothing to do with it), in India the monsoon is somewhat reduced and of course they produce a lot of soot. However, monsoon patterns in India have a lot more to do with global circulation patterns and a lot less to do with local atmospheric factors. The article does not address how BC can affect the former, because of course if it does nobody knows how.
The last irritating thing about the article is that it alleges that BC produced in the tropics has a profound effect on global average temperatures — based, of course, on its assertion that it doesn’t nucleate clouds while is sister ALMOST BC does so that albedo modulation can be ignored. It makes BC out to be “almost as important as CO_2” in its overall effect on AGW.
Wow, did they really say that? So CO_2 is responsible for only half of the observed global anomaly and the other half is soot? So that we could completely cancel the projected catastrophe from a doubling of CO_2 by eliminating the soot and leaving the CO_2? Oooo, I doubt that they meant to say that, however much they want their studies of soot to be funded and gain as much attention as Demon CO_2. We’re about to see the CAGW wars start where researchers compete for ever more scarce dollars on the basis of claims that what they are studying is a major factor (out of the ‘levnty zillion factors that contribute, usually in unknown ways).
In the end, the article simply shows once again that the problem is too complex for people to make egregious assertions. It speaks of how black carbon is supposedly responsible for a significant decrease in global albedo observed back in the 20th century. However, over the last 15 years global albedo (as measured and now confirmed by NASA experiments) has increased by 6% — enough to cause a roughly 2K drop in global temperature and completely cancel 100% of the increase in temperature post the LIA and last Maunder Minimum.
This in and of itself is ignored in the article, in spite of the fact that the papers confirming this have been out for a while now. Whether the increase in albedo is caused by:
* Modulation of cloud nucleating GCRs that increase the rate of cloud formation.
* Increasing soot from rapidly growing China and India actually increasing global albedo from cloud nucleation, regardless of whether the carbon in that soot is “black” or “almost black” (Bullshit! he sneezes…;-).
* Increases in other aerosols from industrializing nations are doing the same thing.
* The inversion of the PDO has effectively redistributed clouds towards the tropics by shunting cool air further south over supersaturated pacific moisture.
* Other mechanisms known and unknown are causing increased cloud formation — fluctuations in tropical currents, fluctuations in atmospheric circulation patterns, space aliens, deific intervention — we don’t know enough about how clouds are formed in the chaotic turbulent soup of the Earth’s atmosphere to be able to track the chaotic feedback loops that form and break up and reform to produce the cloud cover, hour by hour. We can predict it in the short run, but predicting it in the long run just doesn’t work.
We don’t know why some monsoons are very wet and others are relatively dry, not well enough to predict the monsoon rainfall in India a mere 2-3 years in advance. How then can we detect when it is “anomalous”?
At the moment, the modulation of albedo is the big elephant in the room the CAGW folks are trying to ignore even as it is quietly stamping them to death. They know perfectly well that if it persists, it is going to get very, very cold over the next decade, and stay that way until the albedo goes back down again. And they don’t like any of the possible causes on the list above, because they all confound the story they have told about 20th century GW all being due to anthropogenic CO_2 (and friends, such as “extremely black carbon”).
Why hasn’t the temperature gone up over the last decade and a half? Because the albedo increased, strangely coincident with the decrease in solar magnetic activity with the current quiet solar cycle and consequent increase in GCR levels. Or strangely coincident with the industrialization of the third world and all of the smog they produce. Take your pick. To solve the CAGW problem, perhaps we should burn more coal and adjust those burners to produce more soot just like India and China do! Or resume atmospheric testing of nuclear bombs to get a decent amount of radioactive fallout up there in the stratosphere where it can filter down, nucleating clouds along the way (mid-20th century cooling was strongly coincident with above ground testing of nuclear bombs that dumped enormous amounts of radioactive particulates into the air, hmmm).
We even have a choice between anthropogenic modulation of the albedo and solar modulation of the albedo. In the end, it may not matter which one is correct — the one that gets the most grants is the anthropogenic one because nobody can (yet) control the sun.
rgb

E.M.Smith says:
March 27, 2012 at 4:53 pm
I note again the use of the ‘fuzzy word’ of ‘forcing’ (that I still do not find in my Physics book…) …
______________________________
My definition of the ‘fuzzy word’ … ‘forcing’ is “…a propaganda tool used by the News Media to control human behaviour…” When that definition is used all becomes quite clear.

Obviously some falls out on the surface — that causes surface warming. Any in the air warms that air — either high up or right near the surface. So where is most of it?
No, it doesn’t. Or rather, it does, but only on a very small fraction of the surface — the fraction with a high albedo, e.g. snow or ice. Everywhere else it either vanishes without a trace (the 65% of the Earth’s surface that is ice-free ocean or other bodies of water) or is irrelevant (anyplace with plants where it is washed into the ground underneath the shade canopy, anyplace with an already small albedo).
It might be a factor (even an important factor) in the melting of certain glaciers, it is possible that it is a factor in the reduction of icepack in the NH arctic, it is unlikely that it globally important anywhere but the latter.
Up in the air, as noted in my previous reply (that may or may not have gotten through the “login to post” guardians that now plague my post attempts) I do not believe that we even know the sign of the net cooling or heating effect of soot overall. Certainly given evidence of UAH lower troposphere temperatures holding to falling (even as GISS and HADCRUT work hard to produce the illusion of continuing surface warming in the teeth of a non-warming atmosphere) over the last decade when soot production has held steady to increased, there is little convincing evidence that it is heating even the atmosphere, let alone the surface.
rgb

Steve Richards says:
March 28, 2012 at 1:41 am
The discussion here between Willis Eschenbach and E.M.Smith proves the worth of WUWT.
I suspect many readers have learnt from this discourse.
_________________________
Yes, It is enough to make me bookmark the page since it shines a spot light on a major problem in “Climate Science”
I have barely enough physics background to follow the discussion. Unfortunately that is a heck of a lot more physics than the average Joe who never even took Physics in high school much less a few undergrad college courses.

E.M.Smith says:
March 27, 2012 at 4:53 pm
“I note again the use of the ‘fuzzy word’ of ‘forcing’”
‘forcing’ is what they are trying to do to us. There are those who cannot bear the thought of something changing that is outside of their control. Hence the constant use of the term ‘forcing’, which for them has deep psychological implications.

‘the change in net (down minus up) irradiance…”
This defintion of net (down minus up) appears to be at odds with the definition of net in radiation heat transfer. Net is used to tell us what the difference is of absorbed, transmitted and reflected incident radiated heat. Not just up down watts.

– CO2 catches radiation from the surface, and partly radiated it back to the surface, thus making it warmer. In the process, CO2 makes the atmosphere warmer.
– Black Soot catches radiation coming from the sun, preventing that radiation from reaching the surface, thus making the surface cooler than it would have been. In the process black soot makes the atmosphere warmer.
– Not-So-Black Soot catches some radiation from the sun and reflects some radiation from the sun back to space, thus cooling the surface like black soot, but warming the atmosphere less.
All this is very clear, and it was high time someone spelled it out. Thank you Willis.
There is also another effect.
– Black and Not-So-Black Soot get snowed out on glaciers and Arctic and Antarctic ice.
When the snow/ice melts or sublimates, more and more Soot is concentrated on the surface, catching more and more radiation from the sun, thus warming the surface more and more.
This obviously results in increased melting and sublimation.
– On the other hand, Black an Not So-Black-Soot in the air cause less radiation to reach the surface, thus cooling the snow/ice.
I wonder what the net effect will be.
– Maybe in Amsterdam where I live, slightly cooler winters and temporary warming at the end of winter when the snow melts. Net cooling?
– I expect net warming on the glaciers in Switzerland, where sublimation and melting happen all year round, in between periods when snow falls.
– Polar sea ice. Extremely little sunlight in winter with no effect either way; many hours of weak sunlight in summer. Net warming?
Just to complete the picture.

Thanks to the many contributors that point out the issue of black carbon is quite complex. Let me add another.
When BC intercepts energy from the sun and warms the atmosphere it increases the cooling effect of the GHGs in the atmosphere. Hence, GHGs provide an immediate negative feedback that works 24/7 vs. the heating effect that only works while the sun shines.
The whole issue of BC is probably too complex to model accurately in and of itself. What does that say about GCMs?

When BC intercepts energy from the sun and warms the atmosphere it increases the cooling effect of the GHGs in the atmosphere. Hence, GHGs provide an immediate negative feedback that works 24/7 vs. the heating effect that only works while the sun shines.
The whole issue of BC is probably too complex to model accurately in and of itself. What does that say about GCMs?
In general, I agree. Or perhaps not to complex to model accurately eventually, but we aren’t making progress at building accurate GCMs and will not make further progress until we stop leaving important variables out. If we suppose that solar magnetic state is an important factor for whatever reason — something not empirically unreasonable given the strong correlation over millennia between solar state and global temperature — then models that leave this out aren’t going to get the right answer.
No models will get the right answer until models are built that have the right sort of natural variability without CO_2 variation to describe, let’s say, the Holocene, from the Younger Dryas on, in detail, using as input inferred solar state and some natural processes that have the right order of variability. So far if you tried this with GCMs you’d get a completely absurd result because they all assume that the variation of solar forcing (that word again) is nearly irrelevant. This, in turn, has to be assumed in order to make their models fit Mann. Mann has done the world a favor. By flattening the LIA and MWP out of existence he’s created a target world for the GCMs that never existed, making it rather difficult to fit his fantasy hockey stick and fit the rollercoaster the Holocene temperatures have been for everything but bristlecone pines, so to speak.
The thing that I think deserves the most attention is self-organization a la Prigogene. For reasons that I cannot fathom, I never hear of the world’s climate system described as a self-organized driven thermodynamic system far from equilibrium, in spite of the fact that that is precisely what it is. It is the classic example of the kinds of systems studied by Prigogene, Haken, and many others (creating what amounts to an entire sub-discipline of physics). Turbulent rolls are self-organized thermal structures, and they form because they increase the cooling rate compared to thermally stratified fluids. Winds, high and low pressure systems, the oceanic currents, the global oscillations — all of these are self-organized structures in the Earth’s climate system. All of them are subject to changes over short time scales or long that cannot be explained by any sort of linearization. Structures in this milieu for a while may appear to be quite periodic and follow an “empirical law”, but they can in an instant switch to a different period, have a different shape, merge, move. When they do, everything may reorganize in response.
Willis has pointed this out a few times (and I believe it is alluded to above in the context of the “constructional law”) — the Earth almost certainly responds to any increase in “forcing” by also increasing the rate that it sheds heat. That is, net feedback to any forcing is almost certainly negative because positive feedback is associated with critical instability and there is no evidence of positive critical instability in the Earth’s climate record, recent or prehistoric. However, it would be a lot better to have models that exhibit this negative feedback as a direct outcome of self-organization within the system such that the system opposes externally driven changes everywhere except near critical points.
Critical points, in turn, are immediately apparent by means of the Fluctuation-Dissipation theorem. Basically, near a critical point one expects fluctuations to often grow instead of damp, and to have longer life times. Everything varies more wildly. It takes longer for the system to settle down to an “average” behavior. No such behavior has been observed in concert with post-Dalton warming — if anything the climate system is less volatile in the latter 20th century than it was before.
rgb

I have a couple of questions I would like answered:
1) How come that as Carbon Dioxide (CO2) warms up as it receives “Thermal Radiation” (TR) from the Surface, it (CO2) can send the radiation it has gained back down to whence it came, but as the now Atmospheric Black Carbon (ABC) absorbs TR from the Sun it can not direct its TR towards the surface thus offset any cooling.
2) Is this possibly a little taste of a new “emergency theory” just in case the Earth starts to “really cool down”

To me, it sounds like black carbon creates a “virtual surface” for the planet. It’s like moving the surface of the planet upwards (above the actual surface); which consequently shades and cools the real surface while bringing this “virtual” surface higher into the atmosphere warms everything above it by deflecting light and engaging in convection sooner, like a real surface. You can even define the percentage of virtual surface that’s been created by black carbon using the opacity. If we had complete opacity, the real surface would freeze as it would be like living in a cave with no light getting through and all thermal interactions happening at the “virtual” black carbon surface (air is a poor conductor, so not much heat would reach us beneath, we’d be pretty well insulated).
At least, that’s how it seems to me, and what makes sense of all of the data in my mind. Afterall, soot seems like it’s basically just dirt, but up in the atmosphere and mostly carbon instead of silicon oxides.

During a recent BBC documentary on the Arctic, David Attenborough was lowered down a sink hole in the Greenland ice cap, to show what happens to the surface melt water as it disappears down through 100’s of feet of ice.
But what wasn’t mentioned, and I found very interesting, was the color of the ice as he was lowered a fairly short distance into the hole (30 feet?).
The top few feet showed clear bands of white snow and black dirt, with the bands getting finer with depth. But below this was clear blue ice, with no obvious dirt at all.
So at a guess, airborn black carbon had settled into the snow in recent years, where previously it was pure white snow. And since the program was in part about the effect we’re having on climate, why on Earth was there no mention of this obvious feature of the recent ice layers? Presumably as CO2 is clear, so this can’t be anything to do with climate, can it?

Jim D: If you warm the atmosphere and cool the surface, either or both of two things happen.
What you describe is a pair of opposing feedbacks. What you would get, if you are basically correct, is oscillation up and down from a sort of “set point”. My sense is that such an oscillation is concordant with current knowledge. It’s concordant with Willis Eschenbach’s thermostat hypothesis.

On my planet, that shows that surface temperature and atmospheric temperatures are independent variables. Don’t know how it works on yours.

____________________________
Now you have successfully built up a strawman and beaten it to death.
Any argument can be proven wrong when put into a different scope. But I was talking about your statement on the paper which is about effects of black carbon, not about reflective aerosols. And in scope of forcing caused by black carbon particles, surface and atmospheric forcings are not independent variables.

Kasuha, let me review the bidding. I’d said:

“there is about a 30% chance that their “TOA” forcing, which is atmosphere plus surface, is actually less than zero …”

to which you replied:

That’s true just from mathematical point of view assuming surface and atmospheric forcing are independent variables which they aren’t.

Now you are claiming that my reasoning is faulty because my post is “about effects of black carbon, not about reflective aerosols” … but it’s not. You may be thinking of my previous post called “Extremely Black Carbon”. This one is about semi-reflective aerosols, which is why it’s called “Almost-Black carbon”, meaning somewhat reflective.
More to the point, you object saying that in the “scope of forcing caused by black carbon particles, surface and atmospheric forcings are not independent variables”.
That may or may not be true, but we are talking, not about the independence of the forcings themselves, but the independence of the errors in estimating the forcings. Go back to my claim, which was that there was a 30% chance that those errors in the forcing estimates were sufficient to give a net forcing less than zero.
Those errors in the estimate are assuredly independent, rendering your objection moot.
Regards,
w.

E. M. Smith: Finding that it’s “Unphysical” is just fine with me. It means I can not bother expecting any actual ties to reality. Ive done programming and I can play with ‘toy worlds’, I just prefer not to confuse them with anything real.
You must be a great fan of Schrodinger’s Cat (I don’t know how to do umlauts). Like you, Einstein and Schrodinger objected that to replace a “state” or “particle” with the mean of the distribution of the possibilities did not have physical reality. Yet it is really common in many sciences, as it produces at least a first-order approximation.
Willis Eschenbach’s essay is a presentation of the first-order effects, but not a detailed model of all the details of small variations at places and times, which it also does not claim to be. I don’t “speak for” him, but as a regular reader, I have tell you that he has at other times expressed detailed criticisms, where appropriate, very similar to yours: necessity to consider T^4 power, etc.

I have a couple of questions I would like answered:
1) How come that as Carbon Dioxide (CO2) warms up as it receives “Thermal Radiation” (TR) from the Surface, it (CO2) can send the radiation it has gained back down to whence it came, but as the now Atmospheric Black Carbon (ABC) absorbs TR from the Sun it can not direct its TR towards the surface thus offset any cooling.

Hey, O H, good to hear from you. Answers ‘r’ us, sometimes wrong but rarely uncertain, that’s me …
Black carbon or any other aerosol that absorbs sunlight. does indeed re-radiate the energy in all directions.
But since only half of it goes down, the surface ends up receiving much less radiation than it would have if the sunlight had hit the surface directly. As a result, the surface ends up cooler.

2)Is this possibly a little taste of a new “emergency theory” just in case the Earth starts to “really cool down”

Can’t help with that question, as I’m reluctant to speculate about other people’s motives when I understand so little of my own … but it would have to be included in the differential diagnosis.
My thanks,
w.

To me, it sounds like black carbon creates a “virtual surface” for the planet. It’s like moving the surface of the planet upwards (above the actual surface); which consequently shades and cools the real surface while bringing this “virtual” surface higher into the atmosphere warms everything above it by deflecting light and engaging in convection sooner, like a real surface.

Yes, that’s a useful way to understand it. That’s why the claim that atmospheric BC warms the surface has always seemed specious to me.
w.

During a recent BBC documentary on the Arctic, David Attenborough was lowered down a sink hole in the Greenland ice cap, to show what happens to the surface melt water as it disappears down through 100′s of feet of ice.
But what wasn’t mentioned, and I found very interesting, was the color of the ice as he was lowered a fairly short distance into the hole (30 feet?).
The top few feet showed clear bands of white snow and black dirt, with the bands getting finer with depth. But below this was clear blue ice, with no obvious dirt at all.

Interesting question. My guess is that as the snow is compressed into ice, the included particles become part of the ice itself rather than being lumps of soot and dust mixed into the snow. I suspect that when that happens the optical properties change, rendering any inclusions of soot or dust much less visible. In other words, I think you could make fairly clean looking ice out of visibly dirty snow.
In support of this, I know that layers of dust in the ice itself are generally not visible to the naked eye, despite Al Gore’s specious claim in his movie “Inconvenient Lies” to be able to see them.
w.

rgbatduke says:
Your two posts are really good. Short catalogues of potential research projects, so to speak. You probably will like Isaac Held’s blog: http://www.gfdl.noaa.gov/blog/isaac-held/2011/10/26/19-radiative-convective-equilibrium/
If you already know of those, then I apologize for the redundancy.
One can imagine how such simulations might be inhanced/complicated by adding variaties of ABC effects, as well as how hard that would be to do in practice. Hard, but about the right level of difficulty for a next step, IMHO. All throughout atmospheric science, going from the approximate first-order effects as Willis did here, to detailed studies of processes, entails huge increases in the efforts required.

Wills and EM Smith
I recently saw a post http://perspectives.mvdirona.com/2012/03/17/ILoveSolarPowerBut.aspx by James Hamilton- an IT guy- about the overall effectiveness of PV. Your post and discussion got me to thinking a bit about albedo (Willis’s- ” Note also that the greenhouse gain depends in part on the albedo, since the 235W/m2 in the denominator is after albedo reflections.” ). Specifically James notes: “Let’s focus instead on large datacenters in rural areas where the space can be found. Apple is reported to have cleared trees off of 171 acres of land in order to provide photo voltaic power for 4% of their overall estimate data center consumption. Is that gain worth clearing and consuming 171 acres?”
I am trying to figure out how answer James’s question above. It seems like one should try to include the change in albedo in any evaluation of benefits vs. costs. EM comments about grid cells leads me to this conclusion as well. I think I have a basic understanding on how forcing is required in the climate models vs. my understanding of how the physics, chemistry and biology seems to work at my little ranch/farm. What I am interested in knowing currently is if the climate models allow for the albedo to change with what we humans (or the natural environment) do in response to changes in the incoming energy from the sun or the forcings?
In any case, Thanks for the learning experience! It seems like one should try to include the change in albedo in any evaluation. A recent summary of Severin Borenstein seem important to consider too when looking at the effectiveness of our activities- http://ei.haas.berkeley.edu/pdf/newsletter/2012Spring.pdf
“Likewise, the pollution benefits from renewable energy depend on what type of generation it displaces, which also depends on time and location. Without incorporating these factors, cost-benefit analyses of the alternatives are bound to be misleading. If governments are to implement reasoned renewable generation policy, it will be critical to understand the costs and benefits of these technologies in the context of the electricity systems in which they operate.”…………..

This is very interesting, but the main issue usually discussed about black carbon is it causes melting of the ice and snow. It still does this. Soot landing on ice does not, of course, cause the surface to warm up per se but rather causes the ice to melt as the carbon heats up – (presumably if the ice is not too far below freezing).

1) How come that as Carbon Dioxide (CO2) warms up as it receives “Thermal Radiation” (TR) from the Surface, it (CO2) can send the radiation it has gained back down to whence it came, but as the now Atmospheric Black Carbon (ABC) absorbs TR from the Sun it can not direct its TR towards the surface thus offset any cooling.
All CO_2 does is absorb and reradiate energy in its (fairly wide composite) absorption band(s) in the IR part of the spectrum. As electromagnetic radiation passes a CO_2 molecule, there is a finite probability that the molecule will absorb the radiation (exciting one of its quantum states) and then reradiate it. The catch is that it is likely to reradiate it in a somewhat random direction.
If you’ve ever played pinball, you can then visualize what the world looks like to an “IR photon” (easier to visualize in play than a classical EM wave). Some molecule down on the Earth’s surface kicks it into play just like the spring launcher on a pinball table, headed towards outer space. But noooo, there are too many bumpers in the way! It hits one half a klick up that sends it off at right angles. Now it is heading towards outer space the long way, no chance to escape. But bang! It hits another bumper 300 meters further on! This one deflects it back up again, but now it is heading up and east. 1200 meters in that direction pow, only this time it is deflected back towards the ground.
Maybe it makes it! When it hits the ground it is absorbed, briefly warming the ground where it hits, but then the ground cools by kicking a new photon into play heading at the sky. This one goes 2 klicks before hitting the first bumper, then 1 klick south, then 500 meters up, then 900 meters west, then 2700 meters northwest and up, then… maybe it makes it out the far side headed towards space. Maybe it diffuses by means of many collisions back down to the Earth somewhere else. In any event it now takes far longer (on average) for the humble IR photons in the CO_2 absorption bands to make it out of the Earth’s atmosphere, and a very significant fraction of them return to the Earth’s surface for at least one more visit there (sustaining its emission temperature) along the way.
For what it is worth, the mean free path of our CO_2-resonant photon is actually only around 47 meters — the numbers above were illustrative only. That means that on average the photon won’t make it across half a football field before being scattered. Even travelling at the speed of light (and allowing nothing for the photon is absorbed “in” the CO_2 “bumpers”) it takes 4.5 milliseconds to cross the 8 kilometers of atmosphere for a photon that moves at meters per second (which would usually cross that distance without a collision in 0.027 milliseconds, or roughly 170 times as long). Even this estimate isn’t right — illustrating the problem with doing this any simple way — because the mean free path of the photons gets longer the higher the photon diffuses through the bumpers, so it goes farther and has a greater chance of escaping. In reality the transit is probably somewhere in between the 0.026 milliseconds and 4.5 milliseconds; I’d guestimate it around 1 millisecond but really it should be computed, as should the fraction of return pathways.
This mental picture is important because:
* It is the right mental picture for “downwelling radiation”. of the sky as a vast vertical three dimensional pinball machine with every point on the ground launching a steady stream of pinballs straight up (and no “gravity). Those pinballs enter bumpersville and diffusively bounce around until they either exit at the bottom, to be queued up and fired again, or finally happen to hit a clear pathway to space at the top. At any instant in time, there are far more photon/pinballs in transit (order of 100x as many!) as there are being fired in and/or emerging on the far side because they are being lagged order of 100x the straight-out transit time. Plenty of pinballs are shot straight up only to recoil straight back down at the ground.
“Ground temperature”, BTW, is basically the height of the pile of pinballs that the ground has to fire. Every time a pinball (fired anywhere) bounced back to ground it has to go on the stack for that particular point and be fired again, and in the meantime the stack stays a bit higher than it would if no balls ever returned! Greenhouse warming!
* This is the same general model for the albedo of clouds, why clouds (or aerosols, or black carbon dust) reduce the passage of light visible or invisible through them. Small particulates act like pinball bumpers, “trapping” radiation in caged motion that ultimately rejects a significant fraction of them back the way they came (and thereby reduce the average transmission in the original direction.
* In the case of an open system, where a steady stream of pinballs is being delivered that do not scatter off of the intermediary bumpers (coming in as visible light) but that are transformed on hitting the ground into IR pinballs that do scatter off of the bumpers, where the “fire rate” of the ground launchers is proportional to the height of the stack to the fourth power, the ground quickly steps up its fire rate to compensate until ins (on average) equal outs, where “average” isn’t at all fine grained — most of the time every single point on the Earth’s surface is in imbalance, either net warming or net cooling.
* Just for grins, the mean free path for a photon in the sun is small enough that the diffusion time for a photon produced in the solar interior is (IIRC) around 100,000 years. This creates a hellish thermal differential “greenhouse effect” that helps keep the core hot enough to sustain fusion.
Even so, this is still incomplete and inadequate. Humid air has water molecules that are far more prevalent and active and reduce the mean free path to order or 8 meters! Also, if the CO_2 molecule collides with an air molecule during the time it has absorbed the photon but before it emits it, it can (and will) “heat” the air molecule (transfer energy to it), effectively removing the IR pinball from play as the air radiatively cools entirely differently. Finally, a lot of the energy absorbed in this way (warming of the air) is convected to the top of the troposphere where it transfers back to the CO_2 and is radiated away — there is substantial bulk transport of heat, not just radiative transfer, within the atmosphere. Clouds (present or absent), particulates — everything changes, to where my simple “pinball” metaphor breaks down or becomes as hopelessly complex as the physics.
But this should answer, at least in one easily understandable metaphorical way, your (frequently asked) question. Think of photons as pinballs and CO_2 as bumpers that are dense enough that the pinball can go only 1/200th of the way to the top of the troposphere (where it has a good chance to escape out of play) before hitting one, no matter what direction it goes. That makes it easy to see why photons have a lot harder time making it out, and why many of them are scattered back to the ground before they do (basically reducing the rate of energy transfer out of the ground, the cooling rate, until the ground heats up enough to compensate and keep rates in balance anyway.
rgb

One can imagine how such simulations might be enhanced/complicated by adding varieties of ABC effects, as well as how hard that would be to do in practice. Hard, but about the right level of difficulty for a next step, IMHO. All throughout atmospheric science, going from the approximate first-order effects as Willis did here, to detailed studies of processes, entails huge increases in the efforts required.
I agree. Indeed, my personal area of physics expertise is simulations (that’s why I’m so cynical about GCMs, which are gross differential first order models, in a lot of cases, where the underlying reality is nonlinear, partial differential, stochastic diffusive, and has more control variables than they think that it does.
Like leaving out the albedo change. I mean, why bother publishing it if nobody in climate research are going to respond to this huge news? Albedo isn’t like an adjustment on your deductions on a complex schedule where it is hard to see if you win or lose, it is like changing your tax rate. It directly varies the temperature, far more than any “forcing” change. 2% of the total TOA insolation is enormous, and that’s what changing 0.3 to 0.32 represents. True, it is shrunk a bit by the fourth root in the BB formula, but it still vastly outweighs trivial modulation of the WORST CASE direct CO_2 based warming. Which is why unless it goes back up, it will get much cooler — cooler by degrees C — over the next decade or so as the oceans slowly shed heat. If the albedo is indeed connected to solar magnetic activity, and we are indeed entering a Maunder minimum (next cycle and perhaps the one beyond) then it could be 2050 or later before the albedo returns to “normal”; which will be far less than its 20th century Grand Solar Maximum minimum.
rgb

These discussions seem to me to be among the most important I’ve read. I particularly appreciated the various explanations of ‘forcing’, which was a concept appearing in no physics course or text in my experience, and is therefore one to be treated with a great deal of scepticism.

rgbatduke says:
March 28, 2012 at 2:35 pm
Well written.
One question about this: Also, if the CO_2 molecule collides with an air molecule during the time it has absorbed the photon but before it emits it, it can (and will) “heat” the air molecule (transfer energy to it), effectively removing the IR pinball from play as the air radiatively cools entirely differently.
When this occurs, energy in the excited electrons is transmitted to the air molecule? Right?

rgbatduke says:
March 28, 2012 at 9:23 am
“the Earth almost certainly responds to any increase in “forcing” by also increasing the rate that it sheds heat. That is, net feedback to any forcing is almost certainly negative because positive feedback is associated with critical instability and there is no evidence of positive critical instability in the Earth’s climate record, recent or prehistoric…it would be a lot better to have models that exhibit this negative feedback as a direct outcome of self-organization within the system such that the system opposes externally driven changes everywhere except near critical points.”
Fascinating posts. Presumably, youe quote above offers a good explanation why the Earth’s climate system doesn’t (cannot) respond effectively to the onset of (Milankovitch) ice ages…. And, moreover, it tells us that the real climate risks humanity faces in the (relatively) distant future are: 1) from precipitous cooling (ice age onset) 2) are entirely natural (not man-made) in origin, and 3) we would need to find a way to reversibly (emphasis on that word) override the negative feedbacks in the climate thermoregulator at precisely the right time (or move to the tropics)…?

“rgbatduke says:
March 28, 2012 at 9:23 am
The thing that I think deserves the most attention is self-organization a la Prigogene. For reasons that I cannot fathom, I never hear of the world’s climate system described as a self-organized driven thermodynamic system far from equilibrium, in spite of the fact that that is precisely what it is.”
rgbatduke, do a search for Maximum Entropy Production (MEP) in non-linear / non-equilibrium fluid systems. Many papers on earth climate under MEP by Axel Kleidon, Ralph D. Lorenz and GW Paltridge, like :Entropy Production by Earth System Processes
Also used in studies on other planets and regarding Ice Ages.

OK, so no answers to my questions.
As I understand it, in order for Carbon dioxide to absorb and re-radiate IR wavelength energy, the high frequency visible and UV sunlight has to impact a surface and then be re-radiated as lower frequency IR.
Whilst in a black box conceptual model all of the incident heat will be re-radiated, the Earth is not a black box. Rather it is a complex mix of materials with all sort of properties that affect heat transfer.
Remembering that in such an environment, heat will be transferred by three modes (not one) Radiative, conductive and reflective, the exact amount of heat that will be radiated, depends majorly on the materials that receive the incident sunlight and since two thirds (?) of the planet is liquid this represents one very long term heat store.
True that ultimately, for the planets surface to be in thermal balance all incident heat need to be radiated back into space, but in a complex system, this radiation can take some time and some pretty long pathways.
All of which ultimately leads to weather and climate and since some of the climate cycles are pretty long then it can be hard to be certain what the heat balance is like given a snapshot. Which is what the whole debate is about in the first place.
So as far as black carbon is concerned if it absorbs heat and re-radiates it and assuming it is in the troposphere then I can’t see why this would change much at all. Except that ultimately they will be precipitated onto the surface and some will affect the albedo of snow and ice – much will not, because they will be washed out in rainfall.
As far as aerosols are concerned they clearly have some reflective (albedo) properties which means that they will reduce the incident sunlight on the planets surface, but if there is back carbon about some of that incident sunlight might neverthless be absorbed by these particles.
So the major aerosols are sulphate and nitrate, both of which are soluble so would be removed in precipitation, but are unlikely to darken surfaces, just change the pH of the precipitation. These aerosols can also be removed by dry precipitation with the surface and naturally can be absorbed/react in the oceans and waterways.
Remember that the “brown smog” that we see is not really brown, this is caused by backscatter of certain wavelenghts of sunlight by particles, in much the same way as Rayleigh Scattering in the atmosphere causes blue wavelengths to reach the planets surface – hence we see a blue sky during the day, unless you live in LA where looking directly up at midday gives a white haze, but a brown haze when the sun is lower in the sky or when you are looking across from the mountains.

Sorry, just to add a little more to my comments – White haze means that most wavelenghts of visible light is being reflected back, brown haze merely means that only certain visible wavelengths are being back scattered (reflected). This says very little about UV and whether those frequencies can penetrate aerosols. My guess is that they can to some extent in the same way as they can to some extent when its cloudy. Clouds are not perfect reflectors by the way.

A general comment on the discourses of this thread:
A widely used and well accepted but misleading terminology is “reradiate” or “re-radiate.” Typical statement such as “carbon dioxide absorbs IR then reradiates the energy,” implies that carbon dioxide does not emit IR if it does not absorb first. Radiation physics, as indicated by the SB equation, says that CO2 emits 24/7 as long as its temperature is not 0 K, regardless whether it absorbs or not.
We now have a multiple choice question: Are atmospheric CO2 molecules
1) warmer, 2) cooler or 3) the same than N2 and O2 molecules ?
I wonder how people will answer this question.

Mmm good point though a little pedantic – the point is that CO2 adsorbs infra-red at wavelengths that are within the range of IR wavelengths emitted by the Earth (which must be surface temperature dependent) whilst N2 and O2 molecules presumably don’t (otherwise they’d be greenhouse gases too). That being the case the term re-radiate doesn’t seem too innapropriate. As to the next question – it probably depends on whether the atmosphere is at the same temperature as the Earth’s surface beneath it.
My question back is how does heat get transferred to other molecules if they don’t absorb infrared and gases are not good conductors.

Goldie;
It is a key conception that many have not captured. We all know absorption leads to warming of an object. But this is in reference of before and after absorption of the object, not in reference of an absorbing object with non-radiative objects. For CO2, the temperature before absorption is 0 K, absorption of the Earth radiation warms it to around 200 K.
N2 and O2 do not absorb, so they do not emit. Therefore N2 and O2 will keep the heat they have without losing any. They pass their heat by molecular collisions with CO2 and H2O, which then emit the heat into space. Indeed, CO2 is a cooling agent for the atmosphere. Without so called greenhouse gases, the atmosphere would be far warmer and have a positive lapse rate, as we have observed in the high altitude thermosphere – where CO2 has been souted out due to heavier molecular weight.

When this occurs, energy in the excited electrons is transmitted to the air molecule? Right?
This is one of several things that can occur. When the molecule absorbs the photon, which carries momentum and energy, it recoils. It then holds the energy for a characteristic (exponential decay) time typically on the order of nanoseconds (but highly variable) and re-emits the photon at or near the original frequency (or a cascade of photons at lower frequencies, depending on the coupling of the excited level to lower levels) returning eventually to the ground state. The re-emitted photon is correlated in terms of polarization and emission direction with the original photon, but the original photon is on average unpolarized and on average the new emission direction and polarization are random. As the photon is re-emitted, the atom recoils again, this time in a new direction. The frequencies of the absorbed and emitted photons are tuned and detuned relative to the natural frequency of the level involved by a small amount due to the Doppler shift, a phenomenon called “inhomogeneous broadening”. Collisions that occur introduce random shifts in phase (minimally) and sometimes energy that further alter the frequencies (homogeneous broadening). The observed emission (and absorption) spectrum is thus not infinitely sharp for any given pair of coupled quantum levels, and the line widths do depend on the temperature (inhomogeneous) and pressure (homogeneous).
One thing I don’t understand is the assertion that increasing the CO_2 concentration will somehow alter the size of the CO_2 window by some sort of line broadening mechanism. Homogeneous broadening doesn’t depend on the partial pressure of CO_2, it depends on the mean free time between collisions, which depends on the total pressure and temperature of the atmosphere. It doesn’t matter what molecule it collides with, only that it collides. Similar Doppler broadening doesn’t depend on partial pressure.
In any event yes, when a collision occurs some energy and momentum is transferred from the CO_2 molecule to whatever it collides with. The collision also alters the local field and blurs/mixes quantum levels on both participants in the collision and hence enables electronic energy transfer, but in many/most cases this will be minimal and only have the effect of broadening the CO_2 emission lines (and facilitating absorbing in one level pair but emitting in one or more different ones in the resonant band of nearby levels). The direct transfer maintains thermal equilibrium between the CO_2 and the rest of the gas so they aren’t at different temperatures, so that the “warming” of the CO_2 due to absorption and “cooling” due to emission are shared and it doesn’t become seriously disequilibrated with its surroundings.
Increasing the concentration of CO_2 will reduce the mean free time and path between “bumper collisions” as the photons zig and zag diffusively (on average) outwards. This does in turn increase the “resistance” of the atmosphere to outflowing radiative energy in the relevant bands. It is by no means a linear increase — for one thing, the mean free path cubed is proportional to the volume per molecule, so doubling concentration only reduces the mean free path by around 20%. For another, the mean free path increases rapidly with height. For a third, CO_2 is only one greenhouse gas, and the other — water — is a comparative elephant to the CO_2 hare, with a mean free path a fifth as large already and with specular diffusion through and reflection from big puffy clouds to contend with as well. Finally, the atmosphere is already optically quite thick with respect to CO_2, and the outgoing radiative temperature in the CO_2 band has more to do with the height at which the atmosphere becomes “transparent” to in-band IR, e.g. the mean free path gets large enough that further collisions with bumpers become unlikely for photons emitted in the upward direction. Statistically, photons that diffuse to any given height preferentially diffuse upward at an increasing rate because the atmosphere below them becomes more reflective (on average) than that below them. All of these conspire to make the variation of temperature with CO_2 concentration rather weak once optical thickness is achieved, as it has been a hundred times over. Lifting the radiative height (and hence modulating radiative cooling in the IR band) seems to be more a function of the decadal oscillations and uplifting circulation (it is a big factor in El Nino, for example) than it is CO_2 concentration per se.
A really interesting subject, actually. As I have repeatedly said, a sound skeptical position is not “there is no such thing as the CO_2 based GHE”, as one can directly photograph it in action in TOA IR spectroscopy and fully understand its general mechanism, as I’ve tried to explain. It is its egregious amplification in models that try to include its effect by neglecting other important variables and modulators (enough to be able to explain historical natural variability, for starters) followed by an arbitrary multiplication by a non-observable “sensitivity” that is nothing less than a political fudge factor that will come out to be whatever you want it to be in a model you build so that it does that we should (and usually do) all object to.
All the reliable post 1980 data suggests that climate sensitivity has an upper bound that is slightly less than the lower bound of the earlier IPCC estimates. It is time that these estimates were fixed. If the climate stubbornly persists in cooling or remaining neutral, they will have to be fixed no matter how passionate the political inclinations of the scientist involved. One can only hide the lack of a rise and deviation from predictions based on high sensitivity for so long. It is almost certain, in my opinion, that the sensitivity is actually negative, that the real cause of the late 20th century warming was the grand solar maximum and albedo minimum that occurred then, and that when (eventually) the models are corrected to account for that source of natural, non-anthropogenic variability is accounted for the anthropogenic contribution to warming from the 20th century will end up being order of or less than 0.5C including all feedbacks! This is utterly negligible, and would continue to be negligible extrapolated to an end of the twenty-first century doubling of CO_2, assuming that any warming caused isn’t completely erased by the natural downward variation likely to be associated with the recent increase in bond albedo back to pre-20th century levels and beyond.
rgb

rgb;
What a superb series of posts. Your explanations are much appreciated. You have made explicit and clear many of the positions I have been stumbling towards. I get ignored or hammered every time I insist that “no-feedback sensitivity” is tiny compared to Hokey Team and IPCC estimates, well below 1°. Thank you for justifying my stubbornness!
Not sure if WE will take on board your analysis showing that BC and ABC increase airborne albedo and reduce melt-season snow-cover ground albedo. But it’s worth a shot!
What are the consensual atmospherics at Duke like? Are you a shunned outlier, or representative?

rgbatduke says:
March 29, 2012 at 9:59 am
You wrote a better answer than my question deserved. I was thinking along the lines of “Absorption raises the electrons to higher energy states; emission occurs when they return to the lower state; if there is a collision then the high energy electrons are reduced to lower energy states without emission of photons .” I didn’t know if it was possible, and my ability to formulate a question totally vanished.
Many thanks.

Willis, I find the article deeply disturbing, in part because I think upwelling/downwelling radiation models are virtually impossible to get right without solving a diffusion equation (which nobody does AFAICT), in part because the carbon discussion seems to ignore gross first order effects AND radiative diffusion in the greenhouse bands (where the height the atmospheric carbon absorbs sunlight matters), compounding the error.

Duke, I couldn’t agree more. I merely used Ramanathan’s findings to make a point about the variability of the response of the atmosphere to aerosols, not because I particularly believed them. That’s why I pointed out the error in the forcings of ± 50%.
Ramanathan’s results are important because in so many papers the claim is made that if forcing changes, surface temperature must change. The R2008 findings show this to be false, they show that TOA forcing can increase while surface temperature drops. And that is the sole reason I discussed them, because I have the same considerations you have about the R2008 findings.
My rule is, nature simply isn’t that simple. The height, the size of the particles, all of that matters.
By the way, there is a model that can actually resolve some of this stuff. It’s the brainchild of one man, Mark Jacobson, as good things often are. It’s called GATOR-GCMOM, and it does the stuff the other models only pretend to do.
Yes, at the end of the day it’s still a model … but it’s a reasonable one.
All the best, thanks for the comments,
w.

RE: Hans says:
@ March 29, 2012 at 6:51 pm
———————
Many thanks Hans. I really enjoyed the Introd chapter you linked to (Kleidon & Lorenz) and similarly look forward to reading the papers you subsequently linked to (above). Because I haven’t yet read these, my questions/ points below might either or both be moot and/or uninformed:
Q1 (request really): In a post above you noted that the ice age phenomenon is addressed by the MEP principle in a paper/ chapter. Grateful if you would point me at it if it is not one of the two later links you provided…
Q2. the main problems I have with the ‘Gaia hypothesis’, apart from its unfalsifiability (and thus it does not really qualify as a hypothesis) are two-fold:
1. seems to me the conceptual power of complexity theory is that it provides a paradigm whereby the Earth’s biota can be regarded as an emergent property of the physical universe – not the other way round. Climate stability, as an emergent property of physcs, was obviously necessary before life (biological complexity) could arise (self-organise). Sure, the biota then modifies the atmosphere but the physics necessary to generate complex climates which generate temperature stability must have first been satisifed.
The term Gaia, however, in its varied fuzzy interpretations seems to imply this is the other way round doesn’t it? What additional explanatory value does the Gaia hypothesis provide to an understanding of how complex physical systems such as the Earth’s climate arise and operate? Certainly, prior to the formation of life, none – whereas the thermoregulating behaviour of the Earth’s climate system was clearly pre-requisite to the emergence of life on this planet…
2. The politicisation of climate science seems to me to have been deeply wound up with this ill-defined and untestable term ‘Gaia’. If it wasn’t so fuzzy, if it was a real hypothesis (ie. testable) there would be less cause for concern and the hysteria around CAGW could have been stemmed long ago. There’s a danger isn’t there in fuzzy terms masquerading as scientific hypotheses?
What are your thoughts?

Fascinating posts. Presumably, your quote above offers a good explanation why the Earth’s climate system doesn’t (cannot) respond effectively to the onset of (Milankovitch) ice ages…. And, moreover, it tells us that the real climate risks humanity faces in the (relatively) distant future are: 1) from precipitous cooling (ice age onset) 2) are entirely natural (not man-made) in origin, and 3) we would need to find a way to reversibly (emphasis on that word) override the negative feedbacks in the climate thermoregulator at precisely the right time (or move to the tropics)…?
Ice ages are interesting. The Earth’s climate is currently at least bistable — “cold phase” (glacial, ice age) and “warm phase” (interglacial). The cold phase is more stable, evidenced by spending (very) roughly 90,000 years in cold phase vs 10,000 years in warm phase over the last five or more cycles. I have studied bistable open systems in the context of quantum optics (and have a long Physical Review paper on the subject that presents the results of a microscopic simulation from way back in the 80s) as well as magnetic bistability and critical dynamics, so I do have a pretty good grasp on the kinds of differential systems that can lead to it.
The way that it typically works is that the system exhibits hysteresis (look it up on Wikipedia if need be). Depending on where one is in the parameter space that drives the transition, there may be either only one stable state for the climate — either warm phase or cold phase, only a single stable solution and perturbations will always drive one back to the vicinity of that solution — or there may be two stable solutions (or even more than two, especially in openly chaotic systems which may have many attractors and be multistable, not just bistable).
Where there are two solutions, the one you find yourself in is locally stable. If you perturb the system by “small” amounts, warming or cooling in the case of the Earth’s climate system, it will generally return to the locally stable phase. However, the other phase is also locally stable, and if you perturb it too far in that direction, you will cross a critical line that makes the other phase the locally stable state and rapidly switch to that state whether or not the perturbation ends.
To be explicit, ice has a very high albedo and takes a lot of heat to melt. If one covered the Earth today with (say) ice all the way down to the line marking the maximum glaciation in the last glacial period, it would reflect lots of sunlight without giving it an opportunity to heat the Earth. If the mean albedo increased to (say) 0.4, that would be enough to drop the Earth’s average temperature roughly 10 degrees Kelvin, which in turn might make it cold enough to sustain that ice instead of gradually melting it. If it did, the ice age would persist until something changed to favor gradual melting, e.g. a reduction of the albedo (which would then feed back by melting the ice to reduce it still further) or some other alteration that “raised the local thermostat” to where warm phase was the only stable state.
We have no idea what the parametric boundary is for that sort of bistable transition, but what we do know is that as the unknown underlying parameters that eventually will make the warm phase completely unstable and force the Earth into a completely stable cold phase move in that direction, the system will be bistable and furthermore will have a local stability boundary that gradually gets closer and closer to the stable warm phase norm.
This has two observable effects. One is that it will take smaller perturbations to flip the Earth into cold phase. Because the boundary is a place where the system isn’t strongly driven either way, as perturbations move the Earth towards that boundary, it will spend more and more time there before returning to “normal” temperatures for warm phase. The other is that because the stabilizing “forces” are relatively weakening in the warm phase, all natural fluctuations will tend to have longer lifetimes and greater excursion — the “noise” in the climate system will increase and it will become less predictable. All of these sorts of things are observed in naturally bistable physical systems as they near a critical point (in this case a “first order” critical point).
In that regard, bearing in mind that the timescale of fluctuations is at least decades to centuries for the Earth’s climate system, there are two or three data that should be worrisome to us. First is the LIA. It was the coldest excursion in the entire Holocene, post the Younger Dryas (a cold phase bistable fluctuation that actually drove us back to the disappearing cold phase briefly after a fluctuation had kicked us briefly out of cold phase (but obviously not stably) at the start of the Holocene. This could be because of extreme circumstances in the drivers — the Maunder Minimum — but even a Maunder Minimum might have have created such a large excursion if we were solidly and stably in warm phase. The second is the large and fairly rapid variability of the climate observed over the last 1300 years. Earth has gone from the warm MWP through to “normal” Holocene temperatures (but with fairly large fluctuations, dropped to a 10,000 year minimum and stayed there for close to a century with glacial growth, suggesting that for a while there cold phase was emerging as a stable attractor, then warming briefly to normal to chill again in the Dalton minimum, then warming steadily back to normal and beyond, all in the space of some 400 years.
A large part of this movement has probably been driven by solar state, but we don’t know what actually controls the emergence of warm/cold phase bistability and we are completely clueless about the shape of the stability boundary across the bistable regime (which is probably a bistable surface over a multidimensional space — or worse). You invoke Milankovitch, but this is not a sufficient explanation for the bistability observed. It has the wrong periodicity, for example. It is probably a factor in this multidimensional space, but not the factor.
In that regard, CO_2 may have been rather fortunate — if cold phase is emerging (and of course, the empirical evidence is that it is emergent, although we don’t know when — cold phase stability may already exist and the boundary may already be creeping north towards warm phase temperatures) then warming the Earth, even a little bit, may be stabilizing warm phase, protecting it from potentially critical fluctuations that might flip us to cold phase. It may also have reduced the climate sensitivity (by sharpening the restoring forces that make warm phase stable in the first place. There is a bit of empirical evidence that this is the case (if anything, the frequency and violence of storms and prevalence of drought appears to have diminished a bit compared to very long term data — e.g. the east coast drought in the 1600s that nearly wiped out all the European colonies and a number of indigenous tribes down throughout the southeast). It could also be why the IPCC estimates are wrong — they may be basing their sensitivity assumptions on the variability post LIA (the blade of the hockey stick) without recognizing that this may have been restabilizing the system in warm phase where it had begun to be unstable, so that sensitivity is now actually reduced.
Sadly, beyond this we really have little to no “control” over the Earth’s climate system. If the underlying natural forces that govern the bistability (or multistability) are, as they reasonably must be, slowly moving the Earth’s climate along the downhill path that will eventually force a flip back to the 80,000 year stable cold phase, destabilizing warm phase and making LIA excursions more likely and causing them to take ever longer to return to an every cooler “normal” until one finally crosses that invisible line and conditions favor positive feedback albedo-driven glacial growth back to cold phase, there isn’t a damn thing we can do about it, especially if we don’t even understand the underlying parametric dependences so we can’t even approximately predict when all of this will happen, beyond going “well, the Holocene is 11,000 or so years old, making it probable that it is going to end “soon” (within 1-2000 years) based on the recent previous interglacials and assuming that things now are like things then”.
When it does happen, they way it will happen is probably this. A Maunder Minimum will come along — we could be at the precursor of one right now, looking at a very low solar cycle max followed by a nearly flat cycle or cycles. The albedo will increase (it is already up 6%, to ballpark of 0.32 from 0.30). This will gradually drop average temperature roughly 2K. This will overwhelm any post-LIA warming CO_2 based or not, and e.g. Arctic and Antarctic ice formation will return to normal (first) and then actually increase. Glaciers that have shrunk or remained stable for the last few hundred years will grow.If the ice/permafrost reaches far enough south/north from the poles to start to hit latitudes where it begins to materially affect the mean bond albedo, this will constitute a positive feedback effect that will “resist” glacial melting for at least some decades when the Earth’s solar-driven albedo returns to normal (one hopes) post Maunder Minimum. How long and well it resists will depend on how long the MM lasts and how much ice is laid down while it is there. The Earth will then be somewhat vulnerable, if a stable cold phase attractor has emerged beneath the current warm phase in the parameter space. If a second MM occurs (and/or we’ve stopped generating CO_2 and whatever Anthropogenic component is gradually disappearing) before the glaciers have had a chance to melt back towards normal, a second round of growth might well tip the normal sun albedo to the point that favors glacier growth.
In that event, we could easily be tipped straight over the edge to cold phase. Historical evidence is that when it happens it happens fast, and the reason is that the cold phase attractor has long since emerged as the second bistable state beneath the warm phase, so that it is just a matter of crossing that invisible line to where all natural processes conspire to push the system towards the cold phase attractor and those very forces will then do the work without any additional help. Glaciers will grow every year, increasing the albedo as they march south to further cool the system and move the glacial boundary still further south, until tropical warming balances it and further glaciation is arrested.
This would indeed be a catastrophe. We have no evidence at all that a warmer phase exists as an emergent multistable attractor. We can take a glance at the climate record of the last 50 million years (or longer) and clearly see that if anything, even the warm phase we are now experiencing is relatively unlikely (and unstable) compared to the million year norm, and living on borrowed time. If CO_2 stabilizes us in warm phase for a longer time than it might otherwise last, this is a good thing, not a bad one, because an ice age would kill 2/3 of the Earth’s population in a century between famine and war and drought unless we are able to use technology to do more with less, to learn to live in a civilized way under the conditions that existed during the last ice age.
I do predict this catastrophe, but I have no idea when it might occur. It might now be starting, and by 2112 we could be all iced up. It might not start until 3012. I do think that it is well worthwhile to do work that might illuminate our understanding to where we might be able to predict it, and/or detect its precursor signals (as I outlined above) because that would give us a small chance of actually planning for and coping with it instead of being swept along with the general kill-off of northern temperate ecology, the loss of the Canadian and Siberian and Chinese breadbaskets, the late and early killing frosts, and the inexorable march of the permafrost line south (and north) from the poles. This won’t matter to me — I’ll be dead long before the earliest dates we might gain this understanding and see the precursors — but my great great grandchildren might thank us all then for doing some good science now.
rgb

rgbatduke, do a search for Maximum Entropy Production (MEP) in non-linear / non-equilibrium fluid systems. Many papers on earth climate under MEP by Axel Kleidon, Ralph D. Lorenz and GW Paltridge, like :Entropy Production by Earth System Processes Also used in studies on other planets and regarding Ice Ages.
Interesting. As mentioned in my previous post, assuming bistability (or more), there should exist a differential description of the Earth’s stable state that is (classically) S-shaped in some parameter, with the middle branch of the S unstable (and the stability boundary between the upper and lower stable branches. The basic ODE structures that produce such a shape for open systems being externally driven are actually pretty well known (at least in quantum optics, but of course ODEs are ODEs). I would be very interested in seeing if anybody has a gross macroscopic one or two parameter model with an S-shaped stability line or surface that can at least heuristically describe glacial/interglacial transitions, especially since that line or surface would in principle predict what the stable temperature should be given any set of values for the underlying parameters, a quantity utterly missing in any GCMs or other studies and obviously one that is the sine qua non of any work that should be taken seriously. Without it one knows nothing — seriously. With it one has a foundation for understanding local fluctuations and natural variability. With that one can begin to think about looking at the effects of CO_2 and other minor drivers, given the sound evidence that a) the underlying parameter space of the gross stable branches is by far the major determinant of where we are in the climate cycle and what the temperature outside “should” be, given our non-Markovian climate history; b) natural variability around this generally stable temperature is large — order of 10-20% of the separation of the phases; CO_2 may make an important baseline contribution to the whole curve, but because it is saturated the curve itself is currently rather insensitive even to large changes in CO_2 concentration.
rgb

A widely used and well accepted but misleading terminology is “reradiate” or “re-radiate.” Typical statement such as “carbon dioxide absorbs IR then reradiates the energy,” implies that carbon dioxide does not emit IR if it does not absorb first. Radiation physics, as indicated by the SB equation, says that CO2 emits 24/7 as long as its temperature is not 0 K, regardless whether it absorbs or not.
Yeah, but quantum physics says otherwise. In this debate, quantum physics wins hands down.
If kT is less than the excitation energy of an emitting level, BB radiation will be very small indeed. This guy named Planck, you might recall, worked on this. This is why radiation from O_2 and N_2 is not a major contributor to radiative cooling of the atmosphere in spite of the fact that they are in thermal equilibrium with the CO_2 — it isn’t that they don’t have levels that can radiate, it is that those levels don’t get excited by kT-level collisions. Neither, for the most part, do those of CO_2.
If you doubt this, I refer you directly to TOA IR spectra that make the point conclusively. The CO_2 blocking of surface radiation in the IR bands, and its eventual reradiation at a much colder temperature in those bands is clearly a resonant absorption phenomenon, dominated by scattering and not simple radiative cooling. An atom has no “temperature”. A molecule has no “temperature”. It has some mix of translational and electronic energy. Radiation comes from electronic excitation energies, but most of its “thermal energy” is bound up in translation, and it is the general case that when kT is too small to populate a quantum degree of freedom, those degrees of freedom are not in thermal equilibrium with T. Again, this is all laid out in kiddie physics books, where it explains why monoatomic molecules have 3 degrees of freedom and diatomic molecules generally have 5, in spite of the fact that they should have 7 if one allows for axial rotations and vibrations. At most temperatures the axial rotation and vibratory quantum states are not excited. Tons of evidence (specific heats, etc).
rgb

What are the consensual atmospherics at Duke like? Are you a shunned outlier, or representative?
If you are referring to some sort of battle lines between skeptics and non-skeptics (concerning CAGW) I have no idea — both extremes are present, I’d guess, with the latter represented in the school of the environment but the former around as well.
I’d have to say that I am “invisible”. I don’t, after all, do active research in this (and am too busy to do more than post on WUWT although I am tempted to do a few things if/when I ever have time and support). I teach physics at the Duke Marine Lab during the summers, but have never been braced on some sort of “political correctness” issues regarding CAGW (and cannot imagine that happening at Duke, frankly) or threatened with non-employment in what is an elective gig. Of course I am a damn good teacher of physics (if I do say so myself:-) and both the ML admins and my summer students are extremely pleased with the course I teach there.
I don’t hide my skepticism from students, but I’m not teaching “climate physics” and I don’t generally spend hours going over it all with them, either. I simply direct them towards a few true facts and point out that the “consensus among scientists” isn’t, and that physicists are in any even highly consensus proof, given that our entire discipline has been found to be completely incorrect on multiple occasions in the last 400 years, forcing paradigm shifts to completely new conceptual foundations. Physicists don’t believe in “settled science”, they believe in science that appears to be pretty reliable, so far. It’s better that way. Especially when making egregious statements about the most difficult coupled Navier-Stokes problem in the world in a context where we cannot even predict is gross zeroth order normative behavior or identify all of the critical parameters.
rgb

You wrote a better answer than my question deserved. I was thinking along the lines of “Absorption raises the electrons to higher energy states; emission occurs when they return to the lower state; if there is a collision then the high energy electrons are reduced to lower energy states without emission of photons .” I didn’t know if it was possible, and my ability to formulate a question totally vanished.
It can, as can its inverse, but it requires that be commensurate with the energy differential of the levels involved to be probable. This is where classical assumptions break down. Or it requires the possibility of resonant transfer between commensurate levels in the colliding species.
In a cold gas, collisions simply won’t either excite or de-excite most energy levels available to the molecules, I think. But they can bend them a bit, and if a recoiling molecule has enough translational energy compared to the energy levels involved it becomes more likely. Honestly, I have no idea what constitutes “cold” or “likely” for CO_2 in the temperature range of 170-300 K. I suppose I could figure it out — one needs to guestimate-compare for temperatures in this range to for frequencies in the IR band of CO_2. But I have class in a few minutes and don’t have time to do the lookups and multiplications. Probably somebody has done it for you (and better than I would on the back of an electronic envelope) if you google for it.
rgb

By the way, there is a model that can actually resolve some of this stuff. It’s the brainchild of one man, Mark Jacobson, as good things often are. It’s called GATOR-GCMOM, and it does the stuff the other models only pretend to do.
Yes, at the end of the day it’s still a model … but it’s a reasonable one.
Paper saved, thanks. If I ever do have time to mess with this, I’ll maybe start with this as a base on your recommendation. I’ve already got a few of the GCM sites/codes linked, but don’t think I’d found this one. I do so love large scale computation (and know a lot about simulations and so on) and would guess I can improve any model I look at, but starting with a decent one is a lot better than starting from one that is mostly crap.
And besides, “time” — who am I kidding? I’ll have time when I’m dead, most likely.
rgb

rgbatduke says:
March 30, 2012 at 9:03 am
That post and the one following constitute a major contribution to the debate, IMO. It is an important complement to the static model that is used in “Principles of Planetary Climate” by Raymond T. Pierrehumbert (a book I admire and respect.)

rgbatduke says:
March 30, 2012 at 9:44 am
…
In a cold gas, collisions simply won’t either excite or de-excite most energy levels available to the molecules, I think. But they can bend them a bit, and if a recoiling molecule has enough translational energy compared to the energy levels involved it becomes more likely. Honestly, I have no idea what constitutes “cold” or “likely” for CO_2 in the temperature range of 170-300 K.
…
rgb

Thanks; gives some context to the cite by G&T of Schack:

concrete engineering thermodynamics … an expert in this field, namely Alfred Schack, … showed that the radiative component of heat transfer of CO2, though relevant at the temperatures in combustion chambers, can be neglected at atmospheric temperatures.

RE
rgbatduke says:
@ March 30, 2012 at 9:03 am
———————
Many thanks. Grateful for your time. I won’t pretend to properly understand all you have written but I was able to mostly follow your reasoning (when things get multi-deimensional, I get a bit lost) The whole subject of phase transition, stable states, critical points, complexity and emergent behaviours is really fascinating.
If you are able to link to your Physical Review paper (if publicly availably) I would really appreciate that…
I have this analogy in my mind that is probably not approapriate: petrol motors, even if not well-tuned can idle along well enough if the revs are sufficiently high. If the revs fall below some critical point, a motor begins to splutter and eventually stalls. If the evolution of our sun has been from dim to progressively brighter (increasing revs) might we reasonably expect that the boundary conditions where sputtering and stalling can occur (potential to flip to a cold stable state) will change/ evolve – such that crticial points (in a bistable system) are reached less frequently in the future? That is, entropy produciton motors attain some super-stable state? Or am I thinking complete nonsense?!

“Andrew says:
March 29, 2012 at 11:02 pm
the ice age phenomenon is addressed by the MEP principle in a paper?”
Andrew, a paper I have read is Entropy production and multiple equilibria: the case of the ice-albedo feedback, but a better one might be Orbital forcing and role of the latitudinal insolation/temperature gradient .
And yes, I agree with you on the Gaia hypothesis. I consider this little escapade in that paper as pointing at the fact that the mystified Gaia hypothesis may be explained as just a plain result of thermodynamics with the 2nd Law in particular.
Earth is just a big rock obstructing the solar flux. The radiation hitting earth gives opportunities for this energy to dissipate and increase in entropy. Photons hit the surface and 20 times as many leave as low quality IR photons. Others are converted into heat in the ocean and atmosphere, and this heat has to work its way out through maybe thousand of interlinked thermodynamical, mechanical, chemical and biological processes at various speeds. These are all one way or another following the 2nd Law / MEP and can result in self organisation.
So yes, lot’s of the processes are influenced by one or more other processes through the dynamical way all the different gradients in temperature, pressure and concentration evolve. These form a jungle of feedbacks working as described by Le Chatelier’s principle which is again the 2nd Law. And these feedbacks are negative so you get all these nice balances on earth.

rgb;
“These are all one way or another following the 2nd Law / MEP and can result in self organisation.”
With the interesting refinement of the interventions of biology; the atmosphere’s contents and composition are substantially, or even entirely, the result of life processes.

RE
Hans says:
@ March 30, 2012 at 5:24 pm
—————————–
Many thanks Hans. These look great. Such an exciting area of science: starting to wish I had payed more attention to physics at school… Amazing isn’t it: the sophistication and power of emergent thought arising from the complex brain…

rgbatduke; Many physical laws look similar, but they work only when applied properly in proper situations.
According to the Kirchhoff’s law, an object that absorbs emits, and an object that emits absorbs. N2 and O2 do not emit because they do not absorb. In terms of math equation, ε σT^4 leads to 0 at whatever T if literally ε=0.
Now how to interpret the TOA IR spectra: for the CO2 absorption bands (e.g. 15 um one), the spectra detect the radiation by CO2 molecules within the layer from TOA down its absorption depth; therefore the radiation irradiance is determined by the “average” temperature of CO2 molecules within the layer. One can work out similarly what for the absorption bands for any other radiative gases. For the rest of bands, the spectra detect the radiation from the Earth ground surface.
Now a question arises: if the earth ground surface is filtered (or literally covered with a white cloth) so that there is no radiation for CO2 to absorb, will the TOA IR spectra show 0 over its absorption band 15 um? Of course not, CO2 emits only according to its temperature regardless whether gaining temperature by molecular collision or by absorption.

Kelvin Vaughan says:
March 28, 2012 at 1:57 am
Philip Bradley says:
Most studies show surface cooling and upper troposphere warming during the dry season.
Isn’t that due to less water vapour in the atmosphere?
I should have said,
Most studies show a surface cooling trend and an upper troposphere warming trend during the dry season.

rgb, thanks for a very interesting and informative series of posts.You highlight the role of albedo in moving between stable climate states. Early today in another thread I referenced a paper by Christy that showed a 3C increase in temperatures in California’s Central Valley over the 20th C due to irrigation and albedo changes from irrigation.
Humans have caused large scale albedo changes since hunter gathers 50K years ago started using fire to promote grasslands over forest. This continued with the spread of agriculture and albedo was further affected by large increases in irrigation over the last century. From memory 30% of all arable lands are irrigate today.
These anthropogenic albedo changes aren’t restricted to the land surface. As discussed above particulates are effectively changing the albedo of the troposphere.
Here in Western Australia we have an interesting natural experiment. There is a fence that runs for about a thousand kilometers with unirrigated wheat fields on one side and natural dryland forest on the other side. What is commonly observed in summer is that the forest side has substantial cloud cover, while the wheatfields side has no clouds. The boundary exactly follows the line of the fence.
This paper has a number satellite images showing the albedo and cloud cover differences on either side of the fence.http://researchrepository.murdoch.edu.au/2090/1/Effects_of_land_use_in_Southwest_Australia.pdf
There is a case to be made that solar insolation and albedo changes are the anthropogenic effects that matter in climate change.

Philip Bradley says:
March 31, 2012 at 6:32 pm
“Humans have caused large scale albedo changes since hunter gathers 50K years ago started using fire to promote grasslands over forest. This continued with the spread of agriculture and albedo was further affected by large increases in irrigation over the last century. From memory 30% of all arable lands are irrigate today…”
——————————————————-
But what about all the wetlands that have been drained over the last 2 millenia to facilitate this agriculture (eg. throughout Europe and Asia); the desertification of vast areas (eg. in China, Africa); the disappearence of vast lakes and inland seas (in ex-Soviet Russia)… What effects do these man-made changes have your back-of-envelope albedo calclulations Philip?
To be fair, if you go back to rgb’s comments you will see that he made a big point that the paleoclimatic record shows no evidence of instability via run-away warming… he also emphasised how little we know about what has driven the Earth to flip between warm and cold stable states (assuming teh climate is in a bistable system) over geological time frames prior to humans, indeed, prior to the emergence of any life on this planet…
I think you’re anthropocentric (Gaia) world view overlooks the inconvient truth that the complex climate system moves to it’s own rhythm and we know very little about it.

Andrew says:
March 31, 2012 at 9:04 pm
My point was simply that we humans have made land use changes with local and regional effects on temperature substantially larger than the claimed GHG AGW effect. What the net effect of albedo changes on a global scale is, I have no idea. But they do seem large enough to have a significant effect on global averages.
As for disappeared lakes and inland seas, we have created many thousands of new lakes through dams.
I think this is the first time I have been called a Gaiaist.
FWIIW, I happen to think solar insolation changes due to aerosol, cloud seeding and possibly GCRs, have been at least as a significant effect on measured surface temperatures as GHGs over the last 50 years. What relationship measured surface and troposphere temperatures have to climate warming/cooling is a whole other discussion.
regards

rgbatduke says:
March 30, 2012 at 9:27 am
“A widely used and well accepted but misleading terminology is “reradiate” or “re-radiate.” Typical statement such as “carbon dioxide absorbs IR then reradiates the energy,” implies that carbon dioxide does not emit IR if it does not absorb first. Radiation physics, as indicated by the SB equation, says that CO2 emits 24/7 as long as its temperature is not 0 K, regardless whether it absorbs or not.”
Yeah, but quantum physics says otherwise. In this debate, quantum physics wins hands down.
AgreedIf kT is less than the excitation energy of an emitting level, BB radiation will be very small indeed. This guy named Planck, you might recall, worked on this. This is why radiation from O_2 and N_2 is not a major contributor to radiative cooling of the atmosphere in spite of the fact that they are in thermal equilibrium with the CO_2 — it isn’t that they don’t have levels that can radiate, it is that those levels don’t get excited by kT-level collisions. Neither, for the most part, do those of CO_2.
Absent a dipole N2 and O2 don’t radiate either. That’s why an electrically excited N2 molecule is able to collisionally excite a CO2 molecule in a CO2 laser and the CO2 emits not the N2.If you doubt this, I refer you directly to TOA IR spectra that make the point conclusively. The CO_2 blocking of surface radiation in the IR bands, and its eventual reradiation at a much colder temperature in those bands is clearly a resonant absorption phenomenon, dominated by scattering and not simple radiative cooling. An atom has no “temperature”. A molecule has no “temperature”. It has some mix of translational and electronic energy.
Actually a mix of translational, rotational, vibrational, and electronic energyRadiation comes from , rotational, vibrational, and electronic excitation energies, but most of its “thermal energy” is bound up in translation,
In the case of diatomics yes, but not polyatomics like CO2 and H2O where most of the energy is not in translation. and it is the general case that when kT is too small to populate a quantum degree of freedom, those degrees of freedom are not in thermal equilibrium with T. Again, this is all laid out in kiddie physics books apparently better in chem. Books 😉, where it explains why monoatomic molecules have 3 degrees of freedom and diatomic molecules generally have 5, in spite of the fact that they should have 7 actually 6, it’s 3Nif one allows for axial rotations and vibrations. At most temperatures the axial rotation and vibratory quantum states are not excited.
At room temps the rotational are excited (and a small fraction have excited vibrations too), otherwise the specific heat of diatomics and poly atomics would be the same as monatomics.
The IR absorptions by the GHGs are in the vibrational and rotational levels, not electronic as mentioned in one of the other posts. Tons of evidence (specific heats, etc).
Exactly.

In December, the land surface temperature averages 320.2 K over agricultural areas and 316.6 K over native vegetation areas. Thus the agricultural areas tend to be about 3.6 K warmer than native vegetation areas at this time of the year. Land surface temperature s derived from the high-resolution ASTER images also show similar differences in temperatures between the two vegetation types. The observed gradient in land surface temperatures is very sharp across the bunny fence.

Now a question arises: if the earth ground surface is filtered (or literally covered with a white cloth) so that there is no radiation for CO2 to absorb, will the TOA IR spectra show 0 over its absorption band 15 um? Of course not, CO2 emits only according to its temperature regardless whether gaining temperature by molecular collision or by absorption.
I agree, within limits. Were we disagreeing about something like this? The point is that this is a self-consistent result, to the extent that the scattering is sufficiently multiple that the radiation remains at near-thermal equilibrium on the way up. If you truly cover the ground with a perfectly reflective cloth you will indeed change the temperature of TOA radiation, and not in a good way…;-)
To discuss the equilibrium of radiation plus atoms or molecules, however, is ultimately a problem in quantum stat mech, beginning with the assumption of thermal equilibrium. The point being that when certain rates are highly disparate in an open system, the system is in a state of broken ergodicity and hence is not in thermal equilibrium. These sorts of states happen all of the time — laser dynamics is predicated upon them — and are the reason that CO_2 does help radiate away energy but O_2 and N_2 and He all do not, given the outgoing radiation spectrum from the surface. At a different surface temperature, CO_2 might be a non-factor and O_2 and N_2 might be important (although probably not so much given their less complex spectra).
Again, all of this is perfectly visible in TOA spectra, which is why I think that we agree — if we agree that that spectra accurately reflects the underlying physics, how could we not but agree? Nor am I asserting that my multiple scattering model is a perfect one for upwelling/downwelling radiation — personally I intensely dislike that model from the beginning because it is an open invitation to abuse — but it does help one see how there is radiation redirected back to the surface of the Earth from the blanketing CO_2 fraction, as well as energy “trapped” in a retarded transit from the ground to where the atmosphere becomes optically transparent in the relevant bands. The radiation from those molecules is, as you note, still roughly thermalized with the base temperature of the molecules themselves at that point (from TOA IR spectra) which makes perfect sense.
rgb

To be fair, if you go back to rgb’s comments you will see that he made a big point that the paleoclimatic record shows no evidence of instability via run-away warming…
…from the Earth’s current warm phase state to a still warmer phase. Specifically, this figure:http://en.wikipedia.org/wiki/File:Ice_Age_Temperature.png
shows antarctic ice core derived temperatures over the last 5 cycles — no third phase evident — and:http://commons.wikimedia.org/wiki/File:Five_Myr_Climate_Change.png
shows temperature derived from deep sea sediment cores over the last 5 million years. This figure is positively fascinating, as it shows that the current interglacial temperatures are an excursion back to a warm phase that was stable up to 2.7 million years ago with no stable cold phase attractor. Since then the baseline mean temperature has dropped some 6 degrees Kelvin to ice age as the dominant stable state but with a puzzling return to a very chaotic warm phase (bistability) that has only appeared in the last million years, a bistability that appears to actually be stabilizing with more well defined cold and warm phase states but with very little time spent in warm phase. The interglacials are basically sharp spikes back to warm phase on the time scale of this figure.
There is no evidence whatsoever of a still-warmer phase that is feedback stable in this data. In particular, even when the warm phase was stable four million years ago, the global average temperature was a stable 1.5 K warmer than it is now, with remarkably little excursion or noise.
Personally, I think the best possible thing for the human race would be for the Earth to return to this stable warm phase “permanently”, no matter what the dislocations and cost. The catastrophic probability clearly evident in this figure is that on the scale of this figure, the entire Holocene is a spike away from global temperatures that truly are catastrophic; if I were told that this figure described the energy content of an absolutely arbitrary unknown open system I would immediately conclude that the lower energy state was the more probable, that the system is exhibiting bistability with hysteresis, and that the higher energy state is generically unstable with respect to the lower energy state nearly all of the time.
I’m in the process of writing a review-style article I hope to post to WUWT that will examine what I believe to be a serious risk factor — albedo modulation — that can trigger the transition. I’m busy and don’t know when I will finish, but I’ve already given the punch line for those that are familiar with the formula for a baseline greybody temperature — the 6% increase in albedo observed over the last 15 years corresponds to a drop in the baseline pre-GHE greybody temperature of the Earth of at least 2K. Depending on feedback, this might be further amplified or minimized. If the IPCC estimates of climate sensitivity are correct we can expect this temperature drop to be amplified by a factor of 2 to 5, more than enough to trigger a return to an ice age if the albedo remains so shifted for long enough (at least decades, possibly centuries).
This actually raises the disturbing possibility that ice ages are not due to Milankovitch cycles at all, that orbital resonances and so on are irrelevant to them. The emergence of the stable cold phase — actually, the gradual and systematic depression of the warm phase stable state to a colder stable phase but with increasing noise and recently emergent bistability — shows no sign whatsoever of orbital resonance periodicity until maybe the last million years, where it could well be a chaotic system with a bistable oscillation slaving to a weak non-causal perturbation that is otherwise irrelevant to the primary effect (the emergent nearly stable cold phase).
Could ice ages themselves be predominantly due to positive feedback albedo modulation due to very long timescale variability of the sun? They could. They could indeed. For example, as the sun bobs up and down across the galactic plane, it passes (one presumes) through zones where baseline particulate matter is more or less dense. While much of the small stuff is driven outward by photon pressure, all particles greater than a certain size have a tendency to infall (given the right initial conditions) and might well cause a gradual accretion of solar mass and consequent alteration of solar state. I’d be very interested in Lief’s opinion on this — could the Sun have very long term variability in its magnetic state (that is much more subtle than its surface brightness) that suffices to e.g. cause albedo modulation? Noting well that micrometeorite flux (also a cloud nucleation contributor) should independently increase during precisely the same periods, allowing for multiple channels for cloud albedo modulation to where it triggers positive feedback from glaciation…
rgb

Actually a mix of translational, rotational, vibrational, and electronic energy
Radiation comes from , rotational, vibrational, and electronic excitation energies, but most of its “thermal energy” is bound up in translation,
In the case of diatomics yes, but not polyatomics like CO2 and H2O where most of the energy is not in translation.
and it is the general case that when kT is too small to populate a quantum degree of freedom, those degrees of freedom are not in thermal equilibrium with T. Again, this is all laid out in kiddie physics books apparently better in chem. Books ;-), where it explains why monoatomic molecules have 3 degrees of freedom and diatomic molecules generally have 5, in spite of the fact that they should have 7 actually 6, it’s 3Nif one allows for axial rotations and vibrations. At most temperatures the axial rotation and vibratory quantum states are not excited.
Thanks for the correction — I don’t think as much about polyatomics (partly because they are so complicated:-). As for degrees of freedom, I was counting p_x, p_y, p_z, L_x, L_y, L_z, and k_z. If one visits here:http://en.wikipedia.org/wiki/Degrees_of_freedom_%28physics_and_chemistry%29
(as I did to make sure that I’m not losing my mind:-) while you are correct that at room temperature one generally counts only three translation, two rotation, and one vibration, the reason is that it is very difficult to excite rotation around the (z) axis of symmetry so it is generally not counted. But this itself is a kT argument — it isn’t that the DoF isn’t there, it is that we can almost always neglect it (because its moment of inertia is so very small and because the molecule will probably come apart before we excite the mode thermally). I yes, I know, 3N is the standard textbook answer in the tables, but the actual explanation is that one neglects axial rotation which is there but irrelevant in exactly the same way other degrees of freedom can freeze out and become irrelevant if kT is too small.
But the point — as we seem to agree — is that one can’t pretend a problem in quantum statistical mechanics is a problem in classical statistical mechanics and get the right answer, as Planck demonstrated to usher in the quantum era in the first place. One can use semiclassical reasoning to a point, but that point stops short of saying that O_2 and N_2 will radiate just as much energy as CO_2 molecules that they are in thermal equilibrium with, a Commonly Made Mistake in thread comments on the blog (perhaps in addition to a list of FAQs we need a list of CMMs and their corrections whether or not anybody asks the “question” they should to avoid them:-).
rgb

rgbatduke says:
April 2, 2012 at 10:07 am
This figure is positively fascinating, as it shows that the current interglacial temperatures are an excursion back to a warm phase that was stable up to 2.7 million years ago with no stable cold phase attractor. Since then the baseline mean temperature has dropped some 6 degrees Kelvin to ice age as the dominant stable state but with a puzzling return to a very chaotic warm phase (bistability) that has only appeared in the last million years, a bistability that appears to actually be stabilizing with more well defined cold and warm phase states but with very little time spent in warm phase. The interglacials are basically sharp spikes back to warm phase on the time scale of this figure.
The formation of the Isthmus of Panama about 3 million years ago and the growth of the Himalayas may well have had something to do with that.

FWIIW, I happen to think solar insolation changes due to aerosol, cloud seeding and possibly GCRs, have been at least as a significant effect on measured surface temperatures as GHGs over the last 50 years. What relationship measured surface and troposphere temperatures have to climate warming/cooling is a whole other discussion.
Absolute agreement on my part, although I would be broader than just GCRs. We are just starting to appreciate how much “black junk” there is in the interstellar zones, not to mention the Oort cloud. The sun is also still very much a — ahem — “black” box as far as our ability to fully understand what is going on deep inside it is concerned, although as our ability to look at things like neutrinos improves and dynamo models start to work well enough to be long term predictive (if that ever occurs) and it may well have significant long term variability that feeds the process. But albedo is indeed an omitted variable in GCMs (at least as a variable) because if it weren’t, the GCMs would have been adjusted for the short term increase in albedo observed in the last fifteen years and their predictions would have moved rather radically cooler.
rgb

Jinan Cao says:
March 31, 2012 at 1:55 am
rgbatduke; Many physical laws look similar, but they work only when applied properly in proper situations.
According to the Kirchhoff’s law, an object that absorbs emits, and an object that emits absorbs. N2 and O2 do not emit because they do not absorb. In terms of math equation, ε σT^4 leads to 0 at whatever T if literally ε=0.
Now how to interpret the TOA IR spectra: for the CO2 absorption bands (e.g. 15 um one), the spectra detect the radiation by CO2 molecules within the layer from TOA down its absorption depth; therefore the radiation irradiance is determined by the “average” temperature of CO2 molecules within the layer.
Except that in the lower levels of the troposphere the CO2 band is optically thick so the observed emission is only from the thinner upper levels, so not the average T.

Phil. says:
April 2, 2012 at 10:38 am
Except that in the lower levels of the troposphere the CO2 band is optically thick so the observed emission is only from the thinner upper levels, so not the average T.
I said “the “average” temperature of CO2 molecules within the layer”, not the average temperature of the atmosphere.

rgbatduke says:
April 2, 2012 at 10:23 am
Thanks for the correction — I don’t think as much about polyatomics (partly because they are so complicated:-).
No problem, I generally didn’t work with monatomics because they are so simple. 😉
As for degrees of freedom, I was counting p_x, p_y, p_z, L_x, L_y, L_z, and k_z. If one visits here:http://en.wikipedia.org/wiki/Degrees_of_freedom_%28physics_and_chemistry%29
(as I did to make sure that I’m not losing my mind:-) while you are correct that at room temperature one generally counts only three translation, two rotation, and one vibration, the reason is that it is very difficult to excite rotation around the (z) axis of symmetry so it is generally not counted. But this itself is a kT argument — it isn’t that the DoF isn’t there, it is that we can almost always neglect it (because its moment of inertia is so very small and because the molecule will probably come apart before we excite the mode thermally).
For sure since the moment of Inertia depends on the nuclear dimensions!
I yes, I know, 3N is the standard textbook answer in the tables, but the actual explanation is that one neglects axial rotation which is there but irrelevant in exactly the same way other degrees of freedom can freeze out and become irrelevant if kT is too small.
For nonlinear polyatomics all three rotations exist and you still get 3N. Of course no-one considers electronic dofs either.But the point — as we seem to agree — is that one can’t pretend a problem in quantum statistical mechanics is a problem in classical statistical mechanics and get the right answer, as Planck demonstrated to usher in the quantum era in the first place. One can use semiclassical reasoning to a point, but that point stops short of saying that O_2 and N_2 will radiate just as much energy as CO_2 molecules that they are in thermal equilibrium with, a Commonly Made Mistake in thread comments on the blog (perhaps in addition to a list of FAQs we need a list of CMMs and their corrections whether or not anybody asks the “question” they should to avoid them:-).
I agree absolutely, I’ve lost count of the number of times I’ve been abused for making that point. Welcome to the club, I noticed you fighting the good fight on Tallbloke’s blog, I got banned for quoting N&Z, which contradicted him, so I didn’t go back to see how you made out.

Jinan Cao says:
April 3, 2012 at 3:22 am
Phil. says:
April 2, 2012 at 10:38 am
I said “the “average” temperature of CO2 molecules within the layer”, not the average temperature of the atmosphere.
But you defined the layer as:
“the spectra detect the radiation by CO2 molecules within the layer from TOA down its absorption depth”,
Where’s the bottom of the layer, all the way to the surface?

Phil. says:
April 4, 2012 at 4:40 pm
Jinan Cao says:
April 3, 2012 at 3:22 am
Phil. says:
April 2, 2012 at 10:38 am
I said “the “average” temperature of CO2 molecules within the layer”, not the average temperature of the atmosphere. But you defined the layer as: “the spectra detect the radiation by CO2 molecules within the layer from TOA down its absorption depth”,
Where’s the bottom of the layer, all the way to the surface?
The absorption depth is likely a figure of 1 km or 10 km. Actual value of the absorptin depth needs to be determined according to the Beer’s law, as well as the properties of CO2 such as concentration.

Welcome to the club, I noticed you fighting the good fight on Tallbloke’s blog, I got banned for quoting N&Z, which contradicted him, so I didn’t go back to see how you made out.
I didn’t wait to get banned, I just got tired of my posts being annotated or censored, and yeah, got a bit tired of trying to explain why a dimensionless functional form with totally nonphysical dimensioned quantities embedded was absurd. That and when I finally actually looked up the temperatures and pressures on the rest of Jupiter’s moons and plotted them, they didn’t fall anywhere near the supposed universal curve — including the result for Europa. In fact, it was pretty clear that the numbers were fit to the curve, not the curve to the numbers.
So I quit. N&Z is horse-hockey. So is Jelbring. The kind of thing that gives skeptics a bad name.
It’s a shame, actually. N&Z have one or two good ideas, and if they would stop with them instead of trying to assert a “miracle” curve that is neither a miracle nor a reasonable curve, it might actually contribute to the science instead of diverting a huge amount of energy on an obviously erroneous argument.
But that’s OT for this thread, I suppose. I am a card-carrying skeptic, highly dubious of CAGW, but I do, really, try to keep my skepticism based on sound physics and reasonable argument.
rgb

Robert – well said.
Tallbloke keeps digging his hole deeper and deeper over there. I now have a special category of link title for his “way out there” stuff.
Dragonslayers and the N&Z crowd just aren’t going to help climate skepticism in general, so they must be abandoned along the trail forward.

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